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Re: Core restraints dictionary v 0.0.3 for COMCIFS approval

Looks very useful.  A few typos:

   line 131:  categroy_overview
     should be category_overview

   line 476: _enumeration)range
     should be _enumeration_range

   line 560: data_restr_distance_min_details
     should be data_restr_distance_min_detail

   line 1780: _units_details
     should be _units_detail

   line 2006: _example_details
     should be _example_details

   line 2030:  '     _restr_rigid_body_id'
     should be '_restr_rigid_body_id'

   lines 2065:
     data_restr_rigid_body_site_symmetry_label_
     should be data_restr_rigid_body_site_symmetry

   line 2353:
     data_restr_U_isotropic_weight_param
     should be data_restr_U_iso_weight_param

subject to those corrections, my vote is yes -- well done.

   -- Herbert


At 10:14 PM +1000 9/21/10, James Hester wrote:
>Dear COMCIFS,
>
>Following this email is a new version of the restraints dictionary,
>which has been revised according to Herbert's suggestion and has now
>once again been submitted to COMCIFS for final approval.  The
>dictionary will be considered approved once all voting members have
>voted to approve it, or else no objections have been received in the
>next 6 weeks, whichever occurs first.
>
>James.
>=======================================
>
>##############################################################################
>#                                                                            #
>#           CIF RESTRAINTS AND CONSTRAINTS DICTIONARY VERSION 0.03           #
>#           ------------------------------------------------------           #
>#                                                                            #
># Proposed dictionary code for reporting restraints and constraints in the   #
># core CIF dictionary                                                        #
>#                                                                            #
># This dictionary contains the names and definitions proposed for reporting  #
># restraints and constraints in the Core CIF dictionary                      #
>#                                                                            #
># 2010-09-15                                                                 #
># This dictionary has been approved by the core dictionary maintenance group #
># The items described below have been preseneted for final approvcal by      #
># COMCIFS on behalf of the International Union of Crystallography            #
>#                                                                            #
># Copyright 2010 International Union of Crystallography                      #
>##############################################################################
>
>##############################################################################
>#                                                                            #
># Some notes on the philosophy followed in this dictionary                   #
># --------------------------------------------------------                   #
># A RESTRAINT is a condition used in the refinement of a crystal structure   #
># that requires one or more of the parameters of the refinement to lie       #
># within a certain range.                                                    #
>#                                                                            #
># A CONSTRAINT is a condition used in the refinement of a crystal structure  #
># that requires one or more parameters of the refinement to have a           #
># specific value or be exactly equal to another refined parameter.           #
>#                                                                            #
># The range of values allowed in a restraint is given in this dictionary     #
># by a target value and a weighting parameter, the latter being the          #
># expectation value of the difference between the refined value and          #
># the target.                                                                #
># Constraints are indicated by setting the weighting parameter to zero.      #
>#                                                                            #
># Restraints and constraints are handled in many different ways in different #
># programs.  The actual parameters restrained are determined by the way the  #
># restraint is expressed within the program, and different programs          #
># express the same restraint in different ways.  In this dictionary the      #
># restraints are expressed in a way that is most natural to the description  #
># of the crystal structure which means that the parameters given here        #
># may not correspond to the parameters that were actually restrained.        #
># For example the rigid body constraint is expressed here by listing the     #
># atoms in the rigid body. Distances and angles between them are constant.   #
># For a rigid body the target parameters are the same as the refined         #
># parameters, allowing the target geometry of the rigid body to be found     #
># from the reported atomic coordinates.  However, in order to apply          #
># this constraint in a refinement, either the coordinates of the atoms       #
># in some arbitrary coordinate system, or a sufficient number of geometric   #
># parameters of the body, must be specified.  Since all these methods        #
># preserve the rigid body intact, it is only the result that needs           #
># to be reported, not the details of the method used.                        #
># In this way the description of restraints and constraints has been         #
># kept as simple as possible.                                                #
>#                                                                            #
># The restraints and constraints used are many and varied, and not all       #
># can be given in the forms listed in this dictionary.                       #
># For this reason a general item _restr_special_details has been             #
># provided so that a text description can be given for                       #
># a restraint or constraint that cannot be reported in any other way.        #
>#                                                                            #
># Attention is drawn to existing items in the core dictionary that flag      #
># whether items have been restrained or constrained.                         #
># _atom_site_refinement_flags_adp                                            #
># _atom_site_refinement_flags_occupation                                     #
># _atom_site_refinement_flags_posn                                           #
># _atom_site_restraints                                                      #
>#                                                                            #
>##############################################################################
>
>
>data_on_this_dictionary
>     _dictionary_name            cif_core_restraints.dic
>     _dictionary_version         0.3
>     _dictionary_update          2010-09-15
>     _dictionary_history
>;
>2009-18-10  Following consultations between the user community
>and I.David Brown and
>Ilia Guzei IDB started preparing this dictionary using DDL1 by creating items
>required by distance and angle restraints.
>
>2009-12-09 IDB Completed first draft
>
>2010-01-13 IDB Corrected minor errors detected by IG prior to DMG reveiw
>
>2010-01-14 IDB: Run through vcif by Brian McMahon and corrections made.
>esd replaced by su in _type_conditions
>
>2010-06-03 IDB: U-ISO, U-SIMIILAR
>
>2010-10-15 IDB: The revised rigid body description is added.
>;
>
>#
># This dictionary describes 14 restraints some of which are also constraints.
>#
># 1.  Other restraint or constraint
># 2.  Angle
># 3.  Distance
># 4.  Minimum approach of two atoms
># 5.  Angles restrained to be equal
># 6.  Distances restrained to be equal
># 7.  Torsion angles restrained to be equal
># 8.  Restrained parameter
># 9.  Rigid body
># 10. Atoms lie on a plane
># 11. Torsion angle
># 12. Isotropic atom
># 13. Rigid bond
># 14. Similar atomic displacement parameters
>
>#
>#-------------------------------------------------------------------
># RESTRAINT 1. GENERAL RESTRAINT
>#-------------------------------------------------------------------
>#  A general description of constraints and restraints not covered
>#  by other CIF items.
>#
>#
>######################
>#                    #
>#  RESTR             #
>#                    #
>######################
>#
>data_restr_[]
>     _name                      '_restr_[]'
>     _category                  categroy_overview
>     _type                      null
>     _definition
>;      This category is for describing restraints that cannot be
>        described elsewhere.
>;
>
>data_restr_special_details
>     _name                      '_restr_special_details'
>     _category                  'restr'
>     _type                      char
>     _definition
>;      Text descring any restraint or constraint that cannot be
>        described using any of the the other restraint items.
>        See also _atom_site_restraints.
>;
>
>#
># ----------------------------------------------------------------------------
># RESTRAINT 2. AN ANGLE IS RESTRAINED TO A PREDETERMINED VALUE.
># ----------------------------------------------------------------------------
>#
>####################
>#                  #
>#  RESTR_ANGLE     #
>#                  #
>####################
>
>data_restr_angle_[]
>     _name                '_restr_angle_[]'
>     _category            category_overview
>     _type                      null
>     _definition
>;         Items in this category define angles that were restrained 
>in the final
>refinement.
>;
>    _example
>; loop_
>_restr_angle_atom_site_label_1
>_restr_angle_site_symmetry_1
>_restr_angle_atom_site_label_2
>_restr_angle_atom_site_label_3
>_restr_angle_site_symmetry_3
>_restr_angle_target
>_restr_angle_target_weight_param
>_restr_angle_diff
>_restr_angle_details
>C1 1_555  C2  C3 1_555 120  1   -0.3 'generated by JANA'
>C2 1_555  C3  C4 3_455 120  1.5  0.5 ?
>;
>
>data_restr_angle_atom_site_label_
>     loop_ _name             '_restr_angle_atom_site_label_1'
>                             '_restr_angle_atom_site_label_2'
>                             '_restr_angle_atom_site_label_3'
>     _category               'restr_angle'
>     _type                   char
>     _list                   yes
>     _list_mandatory         yes
>     _list_link_parent       '_atom_site_label'
>     _definition
>; The _atom_site_labels used to define the angle. Atom 2 is at the apex of the
>angle.
>;
>
>data_restr_angle_details
>     _name                      '_restr_angle_details'
>     _category                  'restr_angle'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_angle_atom_site_label_'
>     _definition
>;            A free text description of the restraint.
>;
>data_restr_angle_diff
>     _name                      '_restr_angle_diff'
>     _category                  'restr_angle'
>     _type                      numb
>     _type_conditions           su
>     _list                      yes
>     _list_reference            '_restr_angle_atom_site_label_'
>     _units                     degrees
>     _enumeration_range         0:
>     _definition
>;          The difference between the target and the refined angle
>;
>
>data_restr_angle_site_symmetry_
>     loop_ _name              '_restr_angle_site_symmetry_1'
>                              '_restr_angle_site_symmetry_2'
>                              '_restr_angle_site_symmetry_3'
>     _category                  'restr_angle'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_angle_atom_site_label_'
>     loop_ _example
>           _example_detail        .     'no symmetry or translation to site'
>                                  4     '4th symmetry operation applied'
>                                  7_645 '7th symm. posn.; +a on x; -b on y'
>     _enumeration_default         1_555
>     _definition
>;          The symmetry transformation needed to generate the coordinates
>            of the three atoms that define the angle.
>
>               The symmetry code of each atom site as the symmetry-equivalent
>                position number 'n' and the cell translation number 'klm'.
>                These numbers are combined to form the code n_klm.
>                The character string n_klm is composed as follows:
>
>                n refers to the symmetry operation that is applied to the
>                coordinates stored in _atom_site_fract_x, _atom_site_fract_y
>                and _atom_site_fract_z. It should match a number given in
>                _space_group_symop_id.
>
>                k, l and m refer to the translations that are subsequently
>                applied to the symmetry-transformed coordinates to generate
>                the atom used in calculating the angle. These translations
>                (x,y,z) are related to (k,l,m) by the relations
>                     k = 5 +
>                     l = 5 + y
>                     m = 5 + z
>                By adding 5 to the translations, the use of negative numbers
>                is avoided.
>;
>
>data_restr_angle_target
>     _name                      '_restr_angle_target'
>     _category                  'restr_angle'
>     _type                      numb
>     _list                      yes
>     _list_reference            '_restr_angle_atom_site_label_'
>     _units                     degrees
>     _enumeration_range         0:180
>     _definition
>;          The expectation angle defined by the three atoms.
>            This is the target angle for the restrained refinement.
>;
>
>data_restr_angle_target_weight_param
>     _name                      '_restr_angle_target_weight_param'
>     _category                  'restr_angle'
>     _type                      numb
>     _list                      yes
>     _list_reference            '_restr_angle_atom_site_label_'
>     _units                     degrees
>     _enumeration_range         0:180
>     _enumeration_default       0
>     _definition
>;          Weighting parameter = sqrt(1/weight).
>            It is the expectation value of the difference between
>            the refined value and the target.
>            If this parameter is set to zero, the angle will be constrained
>            to refine to the target value.
>            If this item is absent, its value will be taken as zero
>            and the distance will be constrained
>;
>
>#
># ----------------------------------------------------------------------------
># RESTRAINT 3. A DISTANCE IS RESTRAINED TO A PREDETERMINED VALUE.
># ----------------------------------------------------------------------------
>#
>#####################
>#                   #
>#  RESTR_DISTANCE   #
>#                   #
>#####################
>
>data_restr_distance_[]
>     _name                      '_restr_distance_[]'
>     _category                  category_overview
>     _type                      null
>     _definition
>; Category of items that describes restraints applied to distances
>during the final refinement.
>;
>    _example
># - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
>- - - - - -
>;
>loop_
>    _restr_distance_atom_site_label_1
>    _restr_distance_atom_site_label_2
>    _restr_distance_site_symmetry_2
>    _restr_distance_target
>    _restr_distance_target_weight_param
>    _restr_distance_diff
>    _restr_distance_details
>    C1   C2  1_555  1.524  0.04 -0.032 'generated by SHELX DFIX'
>    C2   C3  1_555  1.340  0.04  0.051 'generated by SHELX DFIX'
>    Na1  Ca1 1_555  0.0    0.0   0.0   'Na1 is constrained to occupy Ca site'
>    Fe1  Ca1 1_555  0.0    0.0   0.0  ?
>    Al1  Ca1 1_555  0.0    0.0   0.0  ?
>;
>
>data_restr_distance_atom_site_label_
>     loop_ _name                '_restr_distance_atom_site_label_1'
>                                '_restr_distance_atom_site_label_2'
>     _category                  'restr_distance'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _list_link_parent          '_atom_site_label_'
>     _definition
>; The _atom_site_labels of the two atoms defining the distance to be 
>restrained
>;
>
>data_restr_distance_details
>     _name                      '_restr_distance_details'
>     _category                  'restr_distance'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_distance_atom_site_label_'
>     _definition
>;          A free text description of the restraint.
>;
>
>data_restr_distance_diff
>     _name                      '_restr_distance_diff'
>     _category                  'restr_distance'
>     _type                      numb
>     _list                      yes
>     _list_reference            '_restr_distance_atom_site_label_'
>     _type_conditions           su
>     _units                     A
>     _units_detail              Angstrom
>     _definition
>;          The difference between the target and the refined distance
>;
>
>data_restr_distance_site_symmetry_
>     loop_ _name                '_restr_distance_site_symmetry_1'
>                                '_restr_distance_site_symmetry_2'
>     _category                  'restr_distance'
>     _type                      char
>      _list                      yes
>     _list_reference            '_restr_distance_atom_site_label_'
>     loop_ _example
>           _example_detail        .     'no symmetry or translation to site'
>                                  4     '4th symmetry operation applied'
>                                  7_645 '7th symm. posn.; +a on x; -b on y'
>     _enumeration_default         1_555
>     _definition
>;          The symmetry transformation needed to generate the coordinates
>            of the two atoms that define the distance.
>
>                The symmetry code of each atom site as the symmetry-equivalent
>                position number 'n' and the cell translation number 'klm'.
>                These numbers are combined to form the code n_klm.
>                The character string n_klm is composed as follows:
>
>                n refers to a symmetry operation that is applied to the
>                coordinates stored in _atom_site_fract_x, _atom_site_fract_y
>                and _atom_site_fract_z. It should match a number given in
>                _space_group_symop_id (formerly _symmetry_equiv_pos_site_id).
>
>                k, l and m refer to the translations that are subsequently
>                applied to the symmetry-transformed coordinates to generate
>                the atom used in calculating the distance. These translations
>                (x,y,z) are related to (k,l,m) by the relations
>                     k = 5 + x
>                     l = 5 + y
>                     m = 5 + z
>                By adding 5 to the translations, the use of negative numbers
>                is avoided.
>;
>
>data_restr_distance_target
>     _name                      '_restr_distance_target'
>     _category                  'restr_distance'
>     _type                      numb
>     _list                      yes
>     _list_reference            '_restr_distance_atom_site_label_'
>     _units                     A
>     _units_detail              Angstrom
>     _definition
>;          The expectation distance between the two atoms.
>            This is the target distance for the restrained refinement.
>;
>
>data_restr_distance_target_weight_param
>     _name                      '_restr_distance_target_weight_param'
>     _category                  'restr_distance'
>     _type                      numb
>     _list                      yes
>     _list_reference            '_restr_distance_atom_site_label_'
>     _units                     A
>     _units_detail              Angstrom
>     _enumeration_default       0
>     _definition
>;          Weighting parameter = sqrt(1/weight).
>            It is the expectation value of the difference between
>            the refined value and the target.
>            If this parameter is set to zero, the distance will be constrained
>            to refine to the target value.
>            If this item is absent, its value will be taken as zero
>            and the distance will be constrained
>;
>
>#
># ----------------------------------------------------------------------------
># RESTRAINT 4. ATOMS CANNOT OCCUPY THE SAME POSITION
># ----------------------------------------------------------------------------
># The "anti-bumping" restraint prevents two atoms from occupying the 
>same site.
># It would normally be reported only for those distances
># in which this restraint was invoked.
>#
>###########################
>#                         #
>#  RESTR_DISTANCE_MIN     #
>#                         #
>###########################
>
>data_restr_distance_min_[]
>     _name                      '_restr_distance_min_[]'
>     _category                  category_overview
>     _type                      null
>     _definition
>;  Items in this category offer power law and exponential expressions for
>    a function designed to prevent two atoms occupying the same location.
>;
>     _example
>;
>    loop_
>  _restr_distance_min_atom_site_label_1
>  _restr_distance_min_site_symmetry_1
>  _restr_distance_min_atom_site_label_2
>  _restr_distance_min_site_symmetry_2
>  _restr_distance_min_A
>  _restr_distance_min_B
>  _restr_distance_min_C
>  _restr_distance_min_E
>  _restr_distance_min_F
>  _restr_distance_min_G
>  _restr_distance_min_distance
>  _restr_distance_min_details
>  O1 1_555 O2 1_555 0 . . 1 2.8 0.3 2.75(1) 'using the exponential restraint'
>  O2 1_555 O3 2_455 0 0 0 1 2.8 0   2.83(1) 'using the hard sphere model'
>;
>
>data_restr_distance_min_A
>     _name                      '_restr_distance_min_A'
>     _category                  'restr_distance_min'
>     _type                      numb
>     _list                      yes
>     _list_reference            'restr_distance_min_atomi_site_label_'
>     _enumeration)range         0:
>     _enumeration_default       0
>     _definition
>;  The weight associated with the difference between the refined 
>distance D and
>    the prescribed minimum distance (B or F) is given by the expression:
>
>      w = A*(B/D)^C + E*exp((D-F)/G)
>
>    A and E are dimensionless weighting parameters.
>    Either function could be used alone by setting A or E to zero.
>    The default values of A and E are zero.
>
>    If A=0, B and C are undefined, if E=0, F and G are undefined
>
>    A hard sphere contact can be generated by setting E=1,
>    F=prescribed minimum distance and G=0.  In this case G (combined
>    with a non zero E) should be treated as a flag indicating a hard sphere
>    interaction with a target distance of F so as to avoid division by zero.
>;
>
>data_restr_distance_min_atom_site_label_
>     loop_ _name                      '_restr_distance_min_atom_site_label_1'
>                                '_restr_distance_min_atom_site_label_2'
>     _category                  'restr_distance_min'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _list_link_parent          '_atom_site_label'
>     _definition
>;      _atom_site_labels for the two atoms that are to be kept apart.
>;
>
>data_restr_distance_min_B
>     _name                      '_restr_distance_min_B'
>     _category                  'restr_distance_min'
>     _type                      numb
>     _list                      yes
>     _list_reference            'restr_distance_min_atomi_site_label_'
>     _units                     A
>     _units_detail              Angstrom
>     _enumeration_range         0:
>     _enumeration_default       0
>     _definition
>;  The weight associated with the difference between the refined 
>distance D and
>    the prescribed minimum distance (B or F) is given by the expression:
>
>      w = A*(B/D)^C + E*exp((D-F)/G)
>
>    A and E are dimensionless weighting parameters.
>    Either function could be used alone by setting A or E to zero.
>    The default values of A and E are zero.
>
>    If A=0, B and C are undefined, if E=0, F and G are undefined
>
>    A hard sphere contact can be generated by setting E=1,
>    F=prescribed minimum distance and G=0.  In this case G (combined
>    with a non zero E) should be treated as a flag indicating a hard sphere
>    interaction with a target distance of F so as to avoid division by zero.
>;
>
>data_restr_distance_min_C
>     _name                      '_restr_distance_min_C'
>     _category                  'restr_distance_min'
>     _type                      numb
>     _list                      yes
>     _list_reference            'restr_distance_min_atomi_site_label_'
>     _definition
>;  The weight associated with the difference between the refined 
>distance D and
>    the prescribed minimum distance (B or F) is given by the expression:
>
>      w = A*(B/D)^C + E*exp((D-F)/G)
>
>    A and E are dimensionless weighting parameters.
>    Either function could be used alone by setting A or E to zero.
>    The default values of A and E are zero.
>
>    If A=0, B and C are undefined, if E=0, F and G are undefined
>
>    A hard sphere contact can be generated by setting E=1,
>    F=prescribed minimum distance and G=0.  In this case G (combined
>    with a non zero E) should be treated as a flag indicating a hard sphere
>    interaction with a target distance of F so as to avoid division by zero.
>;
>
>data_restr_distance_min_details
>     _name                      '_restr_distance_min_detail'
>     _category                  'restr_distance_min'
>     _type                      char
>     _list                      yes
>     _list_reference            'restr_distance_min_atomi_site_label_'
>     _definition
>;       A text description of the restraint giving details not
>         given elsewhere.
>;
>
>data_restr_distance_min_difference
>     _name                      '_restr_distance_min_difference'
>     _category                  'restr_distance_min'
>     _type                      numb
>     _list                      yes
>     _list_reference            'restr_distance_min_atomi_site_label_'
>     _units                     A
>     _units_detail              Angstrom
>     _definition
>;       The difference in Angstroms between the refined distance of approach
>         of the two atoms and the target distance B or F:
>
>             difference = D - B or D - F
>;
>
>data_restr_distance_min_distance
>     _name                      '_restr_distance_min_distance'
>     _category                  'restr_distance_min'
>     _type                      numb
>     _list                      yes
>     _list_reference            'restr_distance_min_atomi_site_label_'
>     _units                     A
>     _units_detail              Angstrom
>     _enumeration_range         0:
>     _definition
>;    The refined distance, D, between the two atoms.
>;
>
>data_restr_distance_min_E
>     _name                      '_restr_distance_min_E'
>     _category                  'restr_distance_min'
>     _type                      numb
>     _list                      yes
>     _list_reference            'restr_distance_min_atomi_site_label_'
>     _enumeration_default       0
>     _definition
>;  The weight associated with the difference between the refined 
>distance D and
>    the prescribed minimum distance (B or F) is given by the expression:
>
>      w = A*(B/D)^C + E*exp((D-F)/G)
>
>    A and E are dimensionless weighting parameters.
>    Either function could be used alone by setting A or E to zero.
>    The default values of A and E are zero.
>
>    If A=0, B and C are undefined, if E=0, F and G are undefined
>
>    A hard sphere contact can be generated by setting E=1,
>    F=prescribed minimum distance and G=0.  In this case G (combined
>    with a non zero E) should be treated as a flag indicating a hard sphere
>    interaction with a target distance of F so as to avoid division by zero.
>;
>
>data_restr_distance_min_F
>     _name                      '_restr_distance_min_F'
>     _category                  'restr_distance_min'
>     _type                      numb
>     _list                      yes
>     _list_reference            'restr_distance_min_atomi_site_label_'
>     _units                     A
>     _units_detail              Angstrom
>     _enumeration_range         0:
>     _definition
>;  The weight associated with the difference between the refined 
>distance D and
>    the prescribed minimum distance (B or F) is given by the expression:
>
>      w = A*(B/D)^C + E*exp((D-F)/G)
>
>    A and E are dimensionless weighting parameters.
>    Either function could be used alone by setting A or E to zero.
>    The default values of A and E are zero.
>
>    If A=0, B and C are undefined, if E=0, F and G are undefined
>
>    A hard sphere contact can be generated by setting E=1,
>    F=prescribed minimum distance and G=0.  In this case G (combined
>    with a non zero E) should be treated as a flag indicating a hard sphere
>    interaction with a target distance of F so as to avoid division by zero.
>;
>
>data_restr_distance_min_G
>     _name                      '_restr_distance_min_G'
>     _category                  'restr_distance_min'
>     _type                      numb
>     _list                      yes
>     _list_reference            'restr_distance_min_atomi_site_label_'
>     _units                     A
>     _units_detail              Angstrom
>     _definition
>;  The weight associated with the difference between the refined 
>distance D and
>    the prescribed minimum distance (B or F) is given by the expression:
>
>      w = A*(B/D)^C + E*exp((D-F)/G)
>
>    A and E are dimensionless weighting parameters.
>    Either function could be used alone by setting A or E to zero.
>    The default values of A and E are zero.
>
>    If A=0, B and C are undefined, if E=0, F and G are undefined
>
>    A hard sphere contact can be generated by setting E=1,
>    F=prescribed minimum distance and G=0.  In this case G (combined
>    with a non zero E) should be treated as a flag indicating a hard sphere
>    interaction with a target distance of F so as to avoid division by zero.
>;
>
>data_restr_distance_min_site_symmetry_
>     loop_ _name                      '_restr_distance_min_site_symmetry_1'
>                                '_restr_distance_min_site_symmetry_2'
>     _category                  'restr_distance_min'
>     _type                      char
>     _list                      yes
>     _list_reference            'restr_distance_min_atomi_site_label_'
>     _definition
>;         The site symmetries of the two atoms to be kept apart.
>
>                The symmetry code of each atom site as the symmetry-equivalent
>                position number 'n' and the cell translation number 'klm'.
>                These numbers are combined to form the code n_klm.
>                The character string n_klm is composed as follows:
>
>                n refers to the symmetry operation that is applied to the
>                coordinates stored in _atom_site_fract_x, _atom_site_fract_y
>                and _atom_site_fract_z. It should match a number given in
>                _space_group_symop_id.
>
>                k, l and m refer to the translations that are subsequently
>                applied to the symmetry-transformed coordinates to generate
>                the atom that are to be kept apart.  These translations
>                (x,y,z) are related to (k,l,m) by the relations
>                     k = 5 + x
>                     l = 5 + y
>                     m = 5 + z
>                By adding 5 to the translations, the use of negative numbers
>                is avoided.
>;
>
>
>#
># ----------------------------------------------------------------------------
># RESTRAINT 5. SEVERAL ANGLES ARE RESTRAINED TO BE EQUAL.
># ----------------------------------------------------------------------------
># This restraint contains two categories.
># The first defines the angles to be restrained and assigns
># them to different classes that are restrained independently.
># The second category defines the properties of each class.
>#
>#
>##########################
>#                        #
>#  RESTR_EQUAL_ANGLE     #
>#                        #
>##########################
>
>data_restr_equal_angle_[]
>     _name                '_restr_equal_angle_[]'
>     _category            category_overview
>     _type                      null
>     _definition
>;         Items in this category list the atoms defining the angles
>           that are restrained to be equal in the final refinement.
>;
>     _example
>;
>loop_
>_restr_equal_angle_atom_site_label_1
>_restr_equal_angle_site_symmetry_1
>_restr_equal_angle_atom_site_label_2   # Atom 2 is at the apex of the angle
>_restr_equal_angle_site_symmetry_2
>_restr_equal_angle_atom_site_label_3
>_restr_equal_angle_site_symmetry_3
>_restr_equal_angle_class_id
>_restr_equal_angle_details
>C1 1_555  C2  1_555  C3 1_555 1  'Benzene ring with mirror symmetry'
>C2 1_555  C3  1_555  C4 2_655 2  ?
>C4 1_555  C5  1_555  C6 1_555 2  ?
>C5 1_555  C6  1_555  C1 1_555 1  ?
>;
>
>
>data_restr_equal_angle_atom_site_label_
>     loop_ _name       '_restr_equal_angle_atom_site_label_1'
>                       '_restr_equal_angle_atom_site_label_2'
>                       '_restr_equal_angle_atom_site_label_3'
>     _category                  'restr_equal_angle'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _list_link_parent          '_atom_site_label'
>     _definition
>;      The _atom_site_labels of the three atoms that define one of the
>        angles to be restrained to be equal to other angles in
>        the same class.
>;
>
>data_restr_equal_angle_class_id
>     _name                      '_restr_equal_angle_class_id'
>     _category                  'restr_equal_angle'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_equal_angle_atom_site_label_'
>     _enumeration_default       1
>     _definition
>;       A character string identifying the class of equal angles
>         to which this angle belongs.
>;
>
>data_restr_equal_angle_details
>     _name                    '_restr_equal_angle_details'
>     _category                  'restr_equal_angle'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_equal_angle_atom_site_label_'
>     _definition
>;          A text description giving details of an angle in
>            a class of angles that are restrained to be equal.
>;
>
>data_restr_equal_angle_site_symmetry_label_
>     loop_ _name       '_restr_equal_angle_site_symmetry_label_1'
>                       '_restr_equal_angle_site_symmetry_label_2'
>                       '_restr_equal_angle_site_symmetry_label_3'
>     _category                  'restr_equal_angle'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_equal_angle_atom_site_label_'
>     _definition
>;         The site symmetries of the three atoms that define an angle
>           to be restrained to be equal to other angles in the same class.
>
>                The symmetry code of each atom site as the symmetry-equivalent
>                position number 'n' and the cell translation number 'klm'.
>                These numbers are combined to form the code n_klm.
>                The character string n_klm is composed as follows:
>
>                n refers to the symmetry operation that is applied to the
>                coordinates stored in _atom_site_fract_x, _atom_site_fract_y
>                and _atom_site_fract_z. It should match a number given in
>                _space_group_symop_id.
>
>                k, l and m refer to the translations that are subsequently
>                applied to the symmetry-transformed coordinates to generate
>                the atom used in calculating the angle. These translations
>                (x,y,z) are related to (k,l,m) by the relations
>                     k = 5 + x
>                     l = 5 + y
>                     m = 5 + z
>                By adding 5 to the translations, the use of negative numbers
>                is avoided.
>;
>     loop_ _example
>           _example_detail        .     'no symmetry or translation to site'
>                                  4     '4th symmetry operation applied'
>                                  7_645 '7th symm. posn.; +a on x; -b on y'
>     _enumeration_default         1_555
>
>
>
>###################################
>#                                 #
>#  RESTR_EQUAL_ANGLE_CLASS        #
>#                                 #
>###################################
>#
>#
>data_restr_equal_angle_class_[]
>     _name                '_restr_equal_angle_class_[]'
>     _category            category_overview
>     _type                      null
>     _definition
>;         Items in this category give details of the target angles
>           for each class of angles that are restrained to be equal
>           in the final refinement.
>;
>       _example
>;
>loop_
>_restr_equal_angle_class_class_id
>_restr_equal_angle_class_target_weight_param
>_restr_equal_angle_class_average
>_restr_equal_angle_class_esd
>_restr_equal_angle_class_diff_max
>_restr_equal_angle_class_details
>1  0.50  123.52  0.32 0.62  ?
>2  0.50  118.23  0.52 1.43  ?
>;
>
>data_restr_equal_angle_class_average
>     _name                      '_restr_equal_angle_class_average'
>     _category                  'restr_equal_angle_class'
>     _type                      numb
>     _list                      yes
>     _units                     degrees
>     _enumeration_range         0:
>     _definition
>;         The average angle in the class of angles restrained to
>           be the same after refinement.
>;
>
>data_restr_equal_angle_class_class_id
>     _name                      '_restr_equal_angle_class_class_id'
>     _category                  'restr_equal_angle_class'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _list_link_parent         '_restr_equal_angle_class_id'
>     _enumeration_default       1
>     _definition
>;        A character string that identifies the class of angles
>          whose properties are described.
>;
>
>    data_restr_equal_angle_class_details
>     _name                      '_restr_equal_angle_class_details'
>     _category                  'restr_equal_angle_class'
>     _type                      char
>     _list                      yes
>     _definition
>;        A text description giving details of the class of angles that
>          are restrained to be equal.
>;
>
>    data_restr_equal_angle_class_diff_max
>     _name                      '_restr_equal_angle_class_diff_max'
>     _category                  'restr_equal_angle_class'
>     _type                      numb
>     _type_conditions           su
>     _list                      yes
>     _units                     degrees
>     _enumeration_range         0:
>     _definition
>;         The maximum deviation of an angle in the class from the
>           class average after refinement.
>;
>
>data_restr_equal_angle_class_esd
>     _name                      '_restr_equal_angle_class_esd'
>     _category                  'restr_equal_angle_class'
>     _type                      numb
>     _list                      yes
>     _units                     degrees
>     _enumeration_range         0:
>     _definition
>;        The actual estimated standard deviation of the angles in the
>          class from their average after refinement.
>          This number is expected to be similar to the value set for
>              _restr_equal_angle_class_target_weight_param
>;
>
>data_restr_equal_angle_class_target_weight_param
>     _name              '_restr_equal_angle_class_target_weight_param'
>     _category          'restr_equal_angle_class'
>     _type                      numb
>     _list                      yes
>     _units                     degrees
>     _enumeration_range         0:
>     _enumeration_default       0
>     _definition
>;        The weighting parameter = sqrt(1/weight).
>          The expectation value of the estimated standard deviation of the
>          angles in the class from their average after refinement.
>          This value determines the weight assigned to the restraint.
>          If it is zero the angles are constrained to be equal.
>          The default value is zero.
>;
>
>#
># ----------------------------------------------------------------------------
># RESTRAINT 6. SEVERAL DISTANCES ARE RESTRAINED TO BE EQUAL.
># ----------------------------------------------------------------------------
># This restraint contains two categories.
># The first defines the distances to be restrained and assigns
># them to different classes that are restrained independently.
># The second category defines the properties of each class.
>#
>#############################
>#                           #
>#  RESTR_EQUAL_DISTANCE     #
>#                           #
>#############################
>
>data_restr_equal_distance_[]
>     _name                '_restr_equal_distance_[]'
>     _category            category_overview
>     _type                      null
>     _definition
>;         Items in this category list the atoms defining the distances
>           that are restrained to be equal in the final refinement.
>;
>     _example
>;
>loop_
>  _restr_equal_distance_atom_site_label_1
>  _restr_equal_distance_site_symmetry_1
>  _restr_equal_distance_atom_site_label_2
>  _restr_equal_distance_site_symmetry_2
>  _restr_equal_distance_class_id
>  _restr_equal_distance_details
>  C1 1_555  C2  1_555  1  'C1-C2 and C3-C4 are restrained to be equal'
>  C2 1_555  C3  1_555  2  'C2-C3, C4-C5 and C5-C6 are restrained to be equal'
>  C3 1_555  C4  2_655  1  ?
>  C4 1_555  C5  1_555  2  ?
>  C5 1_555  C6  1_555  2  ?
>;
>
>
>data_restr_equal_distance_atom_site_label_
>     loop_ _name       '_restr_equal_distance_atom_site_label_1'
>                       '_restr_equal_distance_atom_site_label_2'
>     _category                  'restr_equal_distance'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _list_link_parent          '_atom_site_label'
>     _definition
>;      The _atom_site_labels of the two atoms that define one of the
>        distances to be restrained to be equal to other distances in
>        the same class.
>;
>
>data_restr_equal_distance_class_id
>     _name                      '_restr_equal_distance_class_id'
>     _category                  'restr_equal_distance'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_equal_distance_atom_site_label_'
>     _enumeration_default       1
>     _definition
>;       A character string identifying the class of equal distances
>         to which this distance belongs.
>;
>
>data_restr_equal_distance_details
>     _name                    '_restr_equal_distance_details'
>     _category                  'restr_equal_distance'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_equal_distance_atom_site_label_'
>     _definition
>;          A text description giving details of a distance in
>            a class of distances that are restrained to be equal.
>;
>
>data_restr_equal_distance_site_symmetry_label_
>     loop_ _name       '_restr_equal_distance_site_symmetry_label_1'
>                       '_restr_equal_distance_site_symmetry_label_2'
>     _category                  'restr_equal_distance'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_equal_distance_atom_site_label_'
>     _definition
>;         The site symmetries of the two atoms that define a distance
>           to be restrained to be equal to other distances in the same class.
>
>                The symmetry code of each atom site as the symmetry-equivalent
>                position number 'n' and the cell translation number 'klm'.
>                These numbers are combined to form the code n_klm.
>                The character string n_klm is composed as follows:
>
>                n refers to the symmetry operation that is applied to the
>                coordinates stored in _atom_site_fract_x, _atom_site_fract_y
>                and _atom_site_fract_z. It must should a number given in
>                _space_group_symop_id.
>
>                k, l and m refer to the translations that are subsequently
>                applied to the symmetry-transformed coordinates to generate
>                the atom used in calculating the distance. These translations
>                (x,y,z) are related to (k,l,m) by the relations
>                     k = 5 + x
>                     l = 5 + y
>                     m = 5 + z
>                By adding 5 to the translations, the use of negative numbers
>                is avoided.
>;
>     loop_ _example
>           _example_detail        .     'no symmetry or translation to site'
>                                  4     '4th symmetry operation applied'
>                                  7_645 '7th symm. posn.; +a on x; -b on y'
>     _enumeration_default         1_555
>
>
>
>###################################
>#                                 #
>#  RESTR_EQUAL_DISTANCE_CLASS     #
>#                                 #
>###################################
>#
>#
>data_restr_equal_distance_class_[]
>     _name                '_restr_equal_distance_class_[]'
>     _category            category_overview
>     _type                      null
>     _definition
>;         Items in this category give details of the target distances
>           for each class of distances that are restrained to be equal
>           in the final refinement.
>;
>       _example
>;
>  loop_
>  _restr_equal_distance_class_class_id
>  _restr_equal_distance_class_target_weight_param
>  _restr_equal_distance_class_average
>  _restr_equal_distance_class_esd
>  _restr_equal_distance_class_diff_max
>  _restr_equal_distance_class_details
>              1  0.04   1.534  0.032  0.053   ?
>              2  0.04   1.338  0.052  0.103   ?
>;
>
>    data_restr_equal_distance_class_average
>     _name                      '_restr_equal_distance_class_average'
>     _category                  'restr_equal_distance_class'
>     _type                      numb
>     _list                      yes
>     _units                     A
>     _units_detail              Angstrom
>     _enumeration_range         0:
>     _definition
>;         The average distance in the class of distances restrained to
>           be the same after refinement.
>;
>    data_restr_equal_distance_class_class_id
>     _name                      '_restr_equal_distance_class_class_id'
>     _category                  'restr_equal_distance_class'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _list_link_parent         '_restr_equal_distance_class_id'
>     _enumeration_default       1
>     _definition
>;        A character string that identifies the class of distances
>          whose properties are described.
>;
>
>    data_restr_equal_distance_class_details
>     _name                      '_restr_equal_distance_class_details'
>     _category                  'restr_equal_distance_class'
>     _type                      char
>     _list                      yes
>     _definition
>;        A text description giving details of the class of distances that
>          are restrained to be equal.
>;
>
>    data_restr_equal_distance_class_diff_max
>     _name                      '_restr_equal_distance_class_diff_max'
>     _category                  'restr_equal_distance_class'
>     _type                      numb
>     _type_conditions           su
>     _list                      yes
>     _units                     A
>     _units_detail              Angstrom
>     _enumeration_range         0:
>     _definition
>;         The maximum deviation of a distance in the class from the
>           class average after refinement.
>;
>
>    data_restr_equal_distance_class_esd
>     _name                      '_restr_equal_distance_class_esd'
>     _category                  'restr_equal_distance_class'
>     _type                      numb
>     _list                      yes
>     _units                     Angstrom
>     _enumeration_range         0:
>     _definition
>;        The actual estimated standard deviation of the distances in the
>          class from their average after refinement.
>          This number is expected to be similar to the value set for
>              _restr_equal_distance_class_target_weight_param
>;
>    data_restr_equal_distance_class_target_weight_param
>     _name              '_restr_equal_distance_class_target_weight_param'
>     _category          'restr_equal_distance_class'
>     _type                      numb
>     _list                      yes
>     _units                     A
>     _units_detail              Angstrom
>     _enumeration_range         0:
>     _enumeration_default       0
>     _definition
>;        The weighting parameter = sqrt(1/weight).
>          The expectation value of the estimated standard deviation of the
>          distances in the class from their average after refinement.
>          This value determines the weight assigned to the restraint.
>          If it is zero the distances are constrained to be equal.
>          The default value is zero.
>;
>
>#
># ----------------------------------------------------------------------------
># RESTRAINT 7. SEVERAL TORSION ANGLES ARE RESTRAINED TO BE EQUAL.
># ----------------------------------------------------------------------------
># This restraint contains two categories.
># The first defines the torsion angles to be restrained and assigns
># them to different classes that are restrained independently.
># The second category defines the properties of each class.
>#
>############################
>#                          #
>#  RESTR_EQUAL_TORSION     #
>#                          #
>############################
>#
>
>data_restr_equal_torsion_[]
>     _name                '_restr_equal_torsion_[]'
>     _category            category_overview
>     _type                      null
>     _definition
>;         Items in this category list the atoms defining the torsion angles
>           that are restrained to be equal in the final refinement.
>;
>     _example
>;
>loop_
>_restr_equal_torsion_atom_site_label_1
>_restr_equal_torsion_site_symmetry_1
>_restr_equal_torsion_atom_site_label_2
>_restr_equal_torsion_site_symmetry_2
>_restr_equal_torsion_atom_site_label_3
>_restr_equal_torsion_site_symmetry_3
>_restr_equal_torsion_atom_site_label_4
>_restr_equal_torsion_site_symmetry_4
>_restr_equal_torsion_class_id
>_restr_equal_torsion_details
>C1 1_555  C2  1_555  C3 1_555  C4 1_555 1 ?
>C5 1_555  C6  1_555  C1 1_555  C2 1_555 1 ?
>;
>
>
>data_restr_equal_torsion_atom_site_label_
>     loop_ _name       '_restr_equal_torsion_atom_site_label_1'
>                       '_restr_equal_torsion_atom_site_label_2'
>                       '_restr_equal_torsion_atom_site_label_3'
>                       '_restr_equal_torsion_atom_site_label_4'
>     _category                  'restr_equal_torsion'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _list_link_parent          '_atom_site_label'
>     _definition
>;      The _atom_site_labels of the four atoms that define one of the
>        torsion angles to be restrained to be equal to other torsion
>        angles in the same class.  The torsion angle is the dihedral angle
>        between the plane defined by atoms 1, 2 and 3, and the plane defined
>        atoms 2, 3 and 4.
>;
>
>data_restr_equal_torsion_class_id
>     _name                      '_restr_equal_torsion_class_id'
>     _category                  'restr_equal_torsion'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_equal_torsion_atom_site_label_'
>     _enumeration_default       1
>     _definition
>;       A character string identifying the class of equal torsion
>         angles to which this torsion angle belongs.
>;
>
>data_restr_equal_torsion_details
>     _name                    '_restr_equal_torsion_details'
>     _category                  'restr_equal_torsion'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_equal_torsion_atom_site_label_'
>     _definition
>;          A text description giving details of a torsion angle in
>            a class of torsion angles that are restrained to be equal.
>;
>
>data_restr_equal_torsion_site_symmetry_label_
>     loop_ _name       '_restr_equal_torsion_site_symmetry_label_1'
>                       '_restr_equal_torsion_site_symmetry_label_2'
>                       '_restr_equal_torsion_site_symmetry_label_3'
>                       '_restr_equal_torsion_site_symmetry_label_4'
>     _category                  'restr_equal_torsion'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_equal_torsion_atom_site_label_'
>     _enumeration_default         1_555
>     _definition
>;         The site symmetries of the four atoms that define a torsion angle
>           to be restrained to be equal to other torsion angles in the
>           same class.
>
>                The symmetry code of each atom site as the symmetry-equivalent
>                position number 'n' and the cell translation number 'klm'.
>                These numbers are combined to form the code n_klm.
>                The character string n_klm is composed as follows:
>
>                n refers to the symmetry operation that is applied to the
>                coordinates stored in _atom_site_fract_x, _atom_site_fract_y
>                and _atom_site_fract_z. It should match a number given in
>                _space_group_symop_id.
>
>                k, l and m refer to the translations that are subsequently
>                applied to the symmetry-transformed coordinates to generate
>                the atom used in calculating the torsion angle.
>                These translations (x,y,z) are related to (k,l,m)
>                by the relations
>                     k = 5 + x
>                     l = 5 + y
>                     m = 5 + z
>                By adding 5 to the translations, the use of negative numbers
>                is avoided.
>;
>     loop_ _example
>           _example_detail        .     'no symmetry or translation to site'
>                                  4     '4th symmetry operation applied'
>                                  7_645 '7th symm. posn.; +a on x; -b on y'
>
>
>
>###################################
>#                                 #
>#  RESTR_EQUAL_TORSION_CLASS      #
>#                                 #
>###################################
>#
>#
>data_restr_equal_torsion_class_[]
>     _name                '_restr_equal_torsion_class_[]'
>     _category            category_overview
>     _type                      null
>     _definition
>;         Items in this category give details of the target torsion
>           nagles for each class of torsion angles that are restrained
>           to be equal in the final refinement.
>;
>       _example
>;
>  loop_
>  _restr_equal_torsion_class_class_id
>  _restr_equal_torsion_class_target_weight_param
>  _restr_equal_torsion_class_average
>  _restr_equal_torsion_class_esd
>  _restr_equal_torsion_class_diff_max
>  _restr_equal_torsion_class_details
>
>  1  0.50  123.52  0.32  0.62 ?
>;
>
>data_restr_equal_torsion_class_average
>     _name                      '_restr_equal_torsion_class_average'
>     _category                  'restr_equal_torsion_class'
>     _type                      numb
>     _list                      yes
>     _units                     degrees
>     _enumeration_range         0:
>     _definition
>;         The average torsion angle in the class of torsion angles
>           restrained to be the same after refinement.
>;
>
>data_restr_equal_torsion_class_class_id
>     _name                      '_restr_equal_torsion_class_class_id'
>     _category                  'restr_equal_torsion_class'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _list_link_parent         '_restr_equal_torsion_class_id'
>     _enumeration_default       1
>     _definition
>;        A character string that identifies the class of torsion
>          angles whose properties are described.
>;
>
>data_restr_equal_torsion_class_details
>     _name                      '_restr_equal_torsion_class_details'
>     _category                  'restr_equal_torsion_class'
>     _type                      char
>     _list                      yes
>     _definition
>;        A text description giving details of the class of torsion
>          angles that are restrained to be equal.
>;
>
>data_restr_equal_torsion_class_diff_max
>     _name                      '_restr_equal_torsion_class_diff_max'
>     _category                  'restr_equal_torsion_class'
>     _type                      numb
>     _type_conditions           su
>     _list                      yes
>     _units                     degrees
>     _enumeration_range         0:
>     _definition
>;         The maximum deviation of a torsion angle in the class from the
>           class average after refinement.
>;
>
>data_restr_equal_torsion_class_esd
>     _name                      '_restr_equal_torsion_class_esd'
>     _category                  'restr_equal_torsion_class'
>     _type                      numb
>     _list                      yes
>     _units                     degrees
>     _enumeration_range         0:
>     _definition
>;        The actual estimated standard deviation of the torsion
>          angles in the class from their average after refinement.
>          This number is expected to be similar to the value set for
>              _restr_equal_torsion_class_target_weight_param
>;
>
>data_restr_equal_torsion_class_target_weight_param
>     _name              '_restr_equal_torsion_class_target_weight_param'
>     _category          'restr_equal_torsion_class'
>     _type                      numb
>     _list                      yes
>     _units                     degrees
>     _enumeration_range         0:
>     _enumeration_default       0
>     _definition
>;        The weighting parameter = sqrt(1/weight).
>          This is the expectation value of the estimated
>          standard deviation (given in _restr_equal_torsion_class_esd)
>          of the torsion angles in the class from their
>          average after refinement.
>          This value determines the weight assigned to the target.
>          If it is zero the torsion angles are constrained to be equal.
>          The default value is zero.
>;
>
>
>
>#
># ----------------------------------------------------------------------------
># RESTRAINT 8. THE SUM OF A GIVEN PARAMETER OF THE SPECIFIED ATOMS IS
># RESTRAINED
># ----------------------------------------------------------------------------
># This restraint, which will normally be used to restrain the total
># occupancy of an atom site, can be used to restrain the value of
>#   SUM(over the specified atoms){PARAMETER*COEFFICIENT}
># where PARAMETER will usually be the occupancy
># (but other allowed quantities such as x, y and z will be specified
># in the enumeration list) and COEFFICIENT is a user defined
># number with a default value of 1.0.
># Two loops are needed to describe this restraint.
>#
>########################
>#                      #
>#  RESTR_PARAMETER     #
>#                      #
>########################
>#
>
>data_restr_parameter_[]
>     _name                      '_restr_parameter_[]'
>     _category                  category_overview
>     _type                      null
>     _definition
>;      This restraint, which will normally be used to restrain the total
>        occupancy of an atom site, can be used to restrain the value of
>        SUM(over the specified atoms){PARAMETER*COEFFICIENT}
>        where PARAMETER will usually be the value of the occupancy
>        (but other allowed quantities such as x, y and z can be specified
>        in the enumeration) and COEFFICIENT is a user defined
>        number with a default value of 1.0.
>        The restraint requires two loops, the first defines the atoms in
>        each sum (class) and the second describes the properties of the class.
>;
>  loop_    _example
>           _example_detail
>#---------------------------------------------------------
>; loop_
>  _restr_parameter_id
>  _restr_parameter_class_id
>  _restr_parameter_atom_site_label
>  _restr_parameter_atom_coefficient
>1 1 O1   1
>2 1 O1a  1
>3 1 O1b  1
>;
>;  These examples should be read in conjunction with the examples
>    given for the loop restr_parameter_class.
>
>    In Class 1 the sites O1, O1a and O1b refer to separate sites
>    over which oxygen is disordered, but which in total contain
>    0.8 oxygen atoms (as defined by _restr_parameter_class_target).
>;
>#-----------------------------------------------------------
>; loop_
>  _restr_parameter_id
>  _restr_parameter_class_id
>  _restr_parameter_atom_site_label
>  _restr_parameter_atom_coefficient
>a 2 Na1  1
>b 2 K1   1
>c 2 Ca1  1
>d 2 Al1  1
>;
>;
>   Class 2 consists of a mixture of Na, K, Ca and Al atoms on the same
>   site with the total occupancy set to 1.0 as defined in
>   _restr_parameter_class_target.
>;
>#------------------------------------------------------------
>; loop_
>  _restr_parameter_id
>  _restr_parameter_class_id
>  _restr_parameter_atom_site_label
>  _restr_parameter_atom_coefficient
>1 3 Na1  1
>2 3 K1   1
>3 3 Ca1  2
>4 3 Al1  3
>;
>;
>  Class 3 consists of the same atoms as Class 2, but by using coefficients
>  equal to the ionic charge, the total charge on the site is
>  restrained to 2.0.
>  Note that the parameter restrained is still the occupancy
>  but the use of coefficients transforms the restraint from
>  occupancy to formal charge.
>;
>#---------------------------------------------------------------
>; loop_
>  _restr_parameter_id
>  _restr_parameter_class_id
>  _restr_parameter_atom_site_label
>  _restr_parameter_atom_coefficient
>1 4 O2   1
>;
>; In Class 4 the y coordinate of O2 is restrained to be close to a
>   pseudo-mirror plane at y = 0.5 (see _restr_parameter_class_target).
>   This example may not have much practical use, but is included
>   to show what can be done with this definition.
>;
>#----------------------------------------------------------------
>; loop_
>  _restr_parameter_id
>  _restr_parameter_class_id
>  _restr_parameter_atom_site_label
>  _restr_parameter_atom_coefficient
>1 5 O3   1
>2 5 O4   1
>;
>;
>   In Class 5 the positions of O3 and O4 are correlated in such a way that
>   these atoms are displaced equal distances from the plane x = 0
>   (i.e., x(O3)+x(O4) = 0)
>;
>#  ---------------------------- end of examples -------------------
>
>data_restr_parameter_atom_coefficient
>     _name                      '_restr_parameter_atom_coefficient'
>     _category                  'restr_parameter'
>     _type                      numb
>     _list                      yes
>     _list_reference             '_restr_parameter_id'
>     _enumeration_default       1
>     _definition
>;         A parameter that scales the qantity being restrained.
>           It can be used to convert a constraint on occupance to
>           a constraint on ionic charge.
>;
>
>data_restr_parameter_atom_site_label
>     _name                      '_restr_parameter_atom_site_label'
>     _category                  'restr_parameter'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_parameter_id'
>     _list_link_parent          '_atom_site_label'
>     _definition
>;      The _atom_site_label for an atom in this class.
>;
>
>data_restr_parameter_class_id
>     _name                      '_restr_parameter_class_id'
>     _category                  'restr_parameter'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_parameter_id'
>     _enumeration_default       '1'
>     _definition
>;        The identifier of the class of restraint applied to the atoms
>;
>
>data_restr_parameter_id
>     _name                      '_restr_parameter_id'
>     _category                  'restr_parameter'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _definition
>;     A unique identifier for each line in a loop
>;
>
>#
>###################################
>#                                 #
>#     RESTR_PARAMETER_CLASS       #
>#                                 #
>###################################
>#
>
>data_restr_parameter_class_[]
>     _name                      '_restr_parameter_class_[]'
>     _category                  category_overview
>     _type                      null
>     _list_reference            '_restr_parameter_class_class_id'
>     _definition
>;      This restraint, which will normally be used to restrain the total
>        occupancy of an atom site, can be used to restrain the value of
>        SUM(over the specified atoms){PARAMETER*COEFFICIENT}
>        where PARAMETER will usually be the value of the occupancy
>        (but other allowed quantities such as x, y and z can be specified
>        in the enumeration) and COEFFICIENT is a user defined
>        number with a default value of 1.0.
>        The restraint requires two loops, the first defines the atoms in
>        each sum (class) and the second describes the properties of the class.
>;
>     _example
># ------------------------------------------------------
>;
>  loop_
>  _restr_parameter_class_class_id
>  _restr_parameter_class_parameter_type
>  _restr_parameter_class_target
>  _restr_parameter_class_target_weight_param
>   _restr_parameter_class_details
>  1 occupancy   0.8  0.01   'total occupation is 0.8'
>  2 occupancy   1.0  0.001  'total occupation is 1.0'
>  3 occupancy   2.0  0.01   'total charge is 2.0'
>  4 position_y  0.5  0.002  'keep close to pseudo-mirror plane'
>  5 position_x  0    0.01   'correlate position of O3 and O4'
>;
>
>     _example_detail
>
>;  This example gives the properties of the five classes given as examples in
>    restr_parameter.
>
>    The _*_class_id is the _list_reference and is the same as _*_class_id
>    in the restr_parameter loop
>
>    The _*_parameter_type indicates the atomic parameter that is restrained.
>
>    _*_target is the target value for the sum of the product of
>    _restr_parameter_atom_coeffcient and the value of the _*_parameter_type
>    for the atom.
>
>    _*_target_weight_sum gives the expectation value of the difference
>    between the target and the refined value of sum(coefficient*parameter)
>
>    _*_details gives a description of the restraint applied
>;
># --------------------------------------------------------------
>
>data_restr_parameter_class_class_id
>     _name                      '_restr_parameter_class_class_id'
>     _category                  'restr_parameter_class'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _list_link_parent          '_restr_parameter_class_id'
>     _enumeration_default       '1'
>     _definition
>;        The class id of the restraint described in this category
>;
>
>data_restr_parameter_class_details
>     _name                      '_restr_parameter_class_details'
>     _category                  'restr_parameter_class'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_parameter_class_class_id'
>     _definition
>;         A text description of the restraint.
>;
>
>data_restr_parameter_class_parameter_type
>     _name                      '_restr_parameter_class_parameter_type'
>     _category                  'restr_parameter_class'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_parameter_class_class_id'
>    loop_
>                         _enumeration    _enumeration_detail
>                        #------------    -------------------
>                          'occupancy'   '_atom_site_occupancy'
>                          'position_x'  '_atom_site_fract_x'
>                          'position_y'  '_atom_site_fract_y'
>                          'position_z'  '_atom_site_fract_z'
>     _definition
>;        A flag that indicates the nature of the value
>          that is being restrained.
>;
>
>data_restr_parameter_class_target
>     _name                      '_restr_parameter_class_target'
>     _category                  'restr_parameter_class'
>     _type                      numb
>     _list                      yes
>     _list_reference            '_restr_parameter_class_class_id'
>     _definition
>;        The target value for the sum of values of the appropriate
>          parameter type multiplied by the _*_target_weight_param.
>;
>
>data_restr_parameter_class_target_weight_param
>     _name                      '_restr_parameter_class_target_weight_param'
>     _category                  'restr_parameter_class'
>     _type                      numb
>     _list                      yes
>     _list_reference            '_restr_parameter_class_class_id'
>     _enumeration_default       0
>     _definition
>;          Weighting parameter = sqrt(1/weight).
>            It is the expectation value of the difference between
>            the refined value of the sum(parameter*coefficient)
>            and the _*_target.
>            If this parameter is set to zero, the sum will be constrained
>            to refine to the target value.
>            If this item is absent, its value will be taken and zero
>            and the distance will be constrained
>;
>
>#
># ----------------------------------------------------------------------------
># RESTRAINT 9. A GROUP OF ATOMS IS RESTRAINED TO LIE ON A PLANE.
># ----------------------------------------------------------------------------
># This restraint contains two categories.
># The first lists the atoms that define each plane, each plane being
># composed of atoms from the same class.
># The second category describes the properties of each plane (class).
>#
>######################
>#                    #
>#  RESTR_PLANE       #
>#                    #
>######################
>#
>
>data_restr_plane_[]
>     _name                      '_restr_plane_[]'
>     _category                  category_Overview
>     _type                      null
>     _definition
>;    Items in this category define the atoms that make up each class of plane.
>;
>     _example
>;
>  loop_
>  _restr_plane_id
>  _restr_plane_atom_site_label
>  _restr_plane_site_symmetry
>  _restr_plane_class_id
>  _restr_plane_target_weight_param
>  _restr_plane_displacement
>  _restr_plane_details
>1 c1 1_555 1 0.02  0.002(1) 'c1 to c4 lie on one plane'
>2 c2 1_555 1 0.02 -0.003(2) ?
>3 c3 1_555 1 0.02 -0.002(1) ?
>4 c4 1_555 1 0.02  0.002(2) ?
>5 c1 2_655 2 0.003  0.004(1) 'c1, c5, c6 and c7 lie on one plane'
>6 c5 1_555 2 0.003 -0.002(2) ?
>7 c6 1_555 2 0.003  0.002(3) ?
>8 c7 1_555 2 0.003 -0.002(2) ?
>;
>
>data_restr_plane_atom_site_label
>     _name                      '_restr_plane_atom_site_label'
>     _category                  'restr_plane'
>     _type                      char
>     _list                      yes
>     _list_reference            ?
>     _list_mandatory            yes
>     _list_link_parent          '_atom_site_label'
>     _definition
>;       An _atom_site_label of one of the atoms that form the plane
>;
>
>data_restr_plane_class_id
>     _name                      '_restr_plane_class_id'
>     _category                  'restr_plane'
>     _type                      char
>     _list                      yes
>     _list_reference            ?
>     _list_mandatory            yes
>     _enumeration_default       1
>     _definition
>;        A character string that identifies the plane
>          to which this atom is constrained.
>;
>
>data_restr_plane_details
>     _name                      '_restr_plane_details'
>     _category                  'restr_plane'
>     _type                      char
>     _list                      yes
>     _list_reference            ?
>     _definition
>;      A text string giving details not described elsewhere.
>;
>
>data_restr_plane_displacement
>     _name                      '_restr_plane_displacement'
>     _category                  'restr_plane'
>     _type                      numb
>     _type_conditions           su
>     _list                      yes
>     _list_reference            ?
>     _units                     A
>     _units_details             Angstrom
>     _enumeration_range         0:
>     _definition
>;         The distance between this atom and the best plane through
>           all the atoms.
>;
>
>data_restr_plane_id
>     _name                      '_restr_plane_id'
>     _category                  'restr_plane'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _enumeration_default       '1'
>     _definition
>;   A unique identifier for each line in the list.
>;
>
>data_restr_plane_site_symmetry
>     _name                      '_restr_plane_site_symmetry'
>     _category                  'restr_plane'
>     _type                      char
>     _list                      yes
>     _list_reference            ?
>     _list_mandatory            yes
>     _enumeration_default       '1_555'
>     _definition
>;         The site symmetries of the atom that helps to define the plane
>           to which it to be restrained.
>
>                The symmetry code of each atom site as the symmetry-equivalent
>                position number 'n' and the cell translation number 'klm'.
>                These numbers are combined to form the code n_klm.
>                The character string n_klm is composed as follows:
>
>                n refers to the symmetry operation that is applied to the
>                coordinates stored in _atom_site_fract_x, _atom_site_fract_y
>                and _atom_site_fract_z. It should match a number given in
>                _space_group_symop_id.
>
>                k, l and m refer to the translations that are subsequently
>                applied to the symmetry-transformed coordinates to generate
>                the atom used in calculating the plane. These translations
>                (x,y,z) are related to (k,l,m) by the relations
>                     k = 5 + x
>                     l = 5 + y
>                     m = 5 + z
>                By adding 5 to the translations, the use of negative numbers
>                is avoided.
>;
>     loop_ _example
>           _example_detail        .     'no symmetry or translation to site'
>                                  4     '4th symmetry operation applied'
>                                  7_645 '7th symm. posn.; +a on x; -b on y'
>
>data_restr_plane_target_weight_param
>     _name                      '_restr_plane_target_weight_param'
>     _category                  'restr_plane'
>     _type                      numb
>     _list                      yes
>     _units                     A
>     _units_detail              Angstrom
>     _enumeration_range         0:
>     _enumeration_default       0.
>     _definition
>;      The weighting parameter = sqrt(1/weight).
>        The expectation value of the distance in Angstroms between this atom
>        and the best plane through all the atoms of the class.
>;
>
>#
>############################
>#                          #
>#  RESTR_PLANE_CLASS       #
>#                          #
>############################
>#
>
>data_restr_plane_class_[]
>     _name                      '_restr_plane_class_[]'
>     _category                  category_overview
>     _type                      null
>     _definition
>;        Items in thiscategory describe the properties of
>          the different groups of atoms that are restrained
>          to form a plain.
>;
>     _example
>;
>  loop_
>  _restr_plane_class_class_id
>  _restr_plane_class_displacement_esd
>  _restr_plane_class_displacement_max_atom_site_label
>  _restr_plane_class_displacement_max_site_symmetry
>  _restr_plane_class_displacement_max
>  _resrt_plane_class_details
>
>  1  0.032  c2 1_555  0.094     'displacements for plane 1'
>  2  0.0021 c1 2_655  0.010     'displacements for plane 2'
>;
>
>data_restr_plane_class_class_id
>     _name                      '_restr_plane_class_class_id'
>     _category                  'restr_plane_class'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _list_link_parent          '_restr_plane_class_id'
>     _enumeration_default       1
>     _definition
>;       The class identifier for the plane whose properties are described
>;
>
>data_restr_plane_class_details
>     _name                      '_restr_plane_class_details'
>     _category                  'restr_plane_class'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_plane_class_class_id'
>     _definition
>;        Text describing any special features of the restraint.
>;
>
>data_restr_plane_class_displacement_esd
>     _name                      '_restr_plane_class_displacement_esd'
>     _category                  'restr_plane_class'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_plane_class_class_id'
>     _units                     A
>     _units_detail              Angstrom
>     _enumeration_range         0:
>     _definition
>;      The observed estimated standard deviation of the atoms from this plane.
>;
>
>data_restr_plane_class_displacement_max
>     _name                      '_restr_plane_class_displacement_max'
>     _category                  'restr_plane_class'
>     _type                      numb
>     _type_conditions           su
>     _list                      yes
>     _list_reference            '_restr_plane_class_class_id'
>     _units                     A
>     _units_detail              Angstrom
>     _enumeration_range         0:
>     _definition
>;      The distance in Angstrom from the plane to the atom furthest
>        removed from the plane.
>;
>
>data_restr_plane_class_displacement_max_atom_site_label
>     _name            '_restr_plane_class_displacement_max_atom_site_label'
>     _category                  'restr_plane_class'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_plane_class_class_id'
>     _list_link_parent          '_atom_site_label'
>     _definition
>;         The _atom_site_label of the atom that lies furthest
>           from the plane defined by this class
>;
>
>data_restr_plane_class_displacement_max_site_symmetry
>     _name            '_restr_plane_class_displacement_max_site_symmetry'
>     _category                  'restr_plane_class'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_plane_class_class_id'
>     _enumeration_default       '1_555'
>     _definition
>;         The site symmetries of the atom that helps to define the plane
>           to which it to be restrained.
>
>                The symmetry code of each atom site as the symmetry-equivalent
>                position number 'n' and the cell translation number 'klm'.
>                These numbers are combined to form the code n_klm.
>                The character string n_klm is composed as follows:
>
>                n refers to the symmetry operation that is applied to the
>                coordinates stored in _atom_site_fract_x, _atom_site_fract_y
>                and _atom_site_fract_z. It should match a number given in
>                _space_group_symop_id.
>
>                k, l and m refer to the translations that are subsequently
>                applied to the symmetry-transformed coordinates to generate
>                the atom furthest from the plane.  These translations
>                (x,y,z) are related to (k,l,m) by the relations
>                     k = 5 + x
>                     l = 5 + y
>                     m = 5 + z
>                By adding 5 to the translations, the use of negative numbers
>                is avoided.
>;
>     loop_ _example
>           _example_detail        .     'no symmetry or translation to site'
>                                  4     '4th symmetry operation applied'
>                                  7_645 '7th symm. posn.; +a on x; -b on y'
>
>#
>#--------------------------------------------------------------
># RESTRAINT 10. ATOMS ARE DEFINED AS BELONGING TO RIGID BODIES
>#--------------------------------------------------------------
>#
>#############################
>#                           #
>#  RESTR_RIGID_BODY         #
>#                           #
>#############################
>
>data_restr_rigid_body_[]
>     _name                '_restr_rigid_body_[]'
>     _category            category_overview
>     _type                      null
>     _definition
>;         Items in this category list the atoms defining the one or
>           more bodies that are constrained to be rigid in the final
>           refinement.  This is done by listing the atom_site_label
>           and symop for each atom in each rigid body.
>
>           Since rigid bodies are only constrained, not restrained,
>           the rigid body is adequately defined by the refined coordinate
>           in the atom_site list. A second category,
>           restr_rigid_body_class, permits a description
>           of each rigid body to be given in a *_details item.
>;
>loop_    _example  _example_details
>;
>loop_
>  _restr_rigid_body_id
>  _restr_rigid_body_atom_site_label
>  _restr_rigid_body_site_symmetry
>  _restr_rigid_body_class_id
>  _restr_rigid_body_details
>1 C1 1_555  1  ?
>2 C2 1_555  1  ?
>3 C3 1_555  1  'C3 is a hinge atom'
>4 C4 1_555	1  'C4 is a hinge atom'
>5 C3 1_555	2  ?
>6 C4 1_555  2  ?
>7 C5 2_555  2  ?
>8 C6 1_555  2  ?
>;
>; The first rigid body contains C1, C2, C3 and C4, the second rigid body
>   contains C3, C4, C5 and C6.  The boond beteeen C3 and C4 is common to both
>   rigid bodies
>;
>
>data_restr_rigid_body_id
>     _name                '     _restr_rigid_body_id'
>     _category                  'restr_rigid_body'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _definition
>;    A unique identifier for each atom in the list of atoms in the
>      restr_rigid_body category
>;
>     _example                   ?
>     _example_detail            ?
>
>
>data_restr_rigid_body_class_id
>     _name                      '_restr_rigid_body_class_id'
>     _category                  'restr_rigid_body'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_rigid_body_id'
>     _enumeration_default       1
>     _definition
>;       A character string identifying a rigid body.
>;
>
>data_restr_rigid_body_atom_site_label
>     _name       '_restr_rigid_body_atom_site_label'
>     _category                  'restr_rigid_body'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_rigid_body_id'
>     _list_link_parent          '_atom_site_label'
>     _definition
>;      The _atom_site_labels of an atom in a rigid body.
>;
>
>data_restr_rigid_body_site_symmetry_label_
>     _name       '_restr_rigid_body_site_symmetry'
>     _category                  'restr_rigid_body'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_rigid_body_id'
>     _definition
>;         The site symmetry of an atom in a rigid body
>
>                The symmetry code of each atom site as the symmetry-equivalent
>                position number 'n' and the cell translation number 'klm'.
>                These numbers are combined to form the code n_klm.
>                The character string n_klm is composed as follows:
>
>                n refers to the symmetry operation that is applied to the
>                coordinates stored in _atom_site_fract_x, _atom_site_fract_y
>                and _atom_site_fract_z. It should the number given in
>                _space_group_symop_id.
>
>                k, l and m refer to the translations that are subsequently
>                applied to the symmetry-transformed coordinates to generate
>                the atom used in calculating the distance. These translations
>                (x,y,z) are related to (k,l,m) by the relations
>                     k = 5 + x
>                     l = 5 + y
>                     m = 5 + z
>                By adding 5 to the translations, the use of negative numbers
>                is avoided.
>;
>     loop_ _example
>           _example_detail        .     'no symmetry or translation applied'
>                                  4     '4th symmetry operation applied'
>                                  7_645 '7th symm. posn.; +1 on x; -1 on y'
>     _enumeration_default         1_555
>
>data_restr_rigid_body_details
>     _name                    '_restr_rigid_body_details'
>     _category                  'restr_rigid_body'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_rigid_body_id'
>     _definition
>;          A text description giving details of a distance in
>            a class of distances that are constrained to be equal.
>;
>
>
>###################################
>#                                 #
>#  RESTR_RIGID_BODY_CLASS         #
>#                                 #
>###################################
>#
>
>data_restr_rigid_body_class_[]
>     _name                '_restr_rigid_body_class_[]'
>     _category            category_overview
>     _type                      null
>     _definition
>;         Items in this category give details of the dfferent rigid
>           bodies as defined by _restr_rigid_body_class_id
>;
>       _example
>;
>  loop_
>  _restr_rigid_body_class_class_id
>  _restr_rigid_body_class_details
>              1   'Phenyl ring'
>              2   'methyl group'
>;
>
>
>    data_restr_rigid_body_class_class_id
>     _name                      '_restr_rigid_body_class_class_id'
>     _category                  'restr_rigid_body_class'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _list_link_parent         '_restr_rigid_body_class_id'
>     _enumeration_default       1
>     _definition
>;        A character string that identifies the rigid body.
>          It must match one of the values of _restr_rigid_body_class_id
>;
>
>    data_restr_rigid_body_class_details
>     _name                      '_restr_rigid_body_class_details'
>     _category                  'restr_rigid_body_class'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_rigid_body_class_class_id'
>     _definition
>;        A text description giving details of a rigid body.
>;
>
># ----------------------------------------------------------------------------
># RESTRAINT 11. A TORSION ANGLE IS CONSTRAINED TO A PREDETERMINED VALUE
># ----------------------------------------------------------------------------
>#
>######################
>#                    #
>#  RESTR_TORSION     #
>#                    #
>######################
>
>data_restr_torsion_[]
>     _name                '_restr_torsion_[]'
>     _category            category_overview
>     _type                      null
>     _definition
>;         Items in this category define torsion angles that were restrained
>           in the final refinement.
>;
>loop_    _example
>          _example_detail
>;  _restr_torsion_atom_site_label_1
>    _restr_torsion_site_symmetry_1
>    _restr_torsion_atom_site_label_2
>    _restr_torsion_site_symmetry_2
>    _restr_torsion_atom_site_label_3
>    _restr_torsion_site_symmetry_3
>    _restr_torsion_atom_site_label_4
>    _restr_torsion_site_symmetry_4
>    _restr_torsion_angle
>    _restr_torsion_weight_param
>    _restr_torsion_diff
>    _restr_torsion_details
>  Na1 1_555  Na1 2_555  O1 2_555  H101 1_555  90  1  0.97  ?
>;
>; An example of a torsion angle restrained to 90+/-1 degree with a refined
>  difference of 0.97 degrees.
>;
>
>data_restr_torsion_angle_target
>     _name                      '_restr_torsion_angle_target'
>     _category                  'restr_torsion'
>     _type                      numb
>     _list                      yes
>     _list_reference            '_restr_torsion_atom_site_label_'
>     _units                       degree
>     _enumeration_range         -180:180
>     _definition
>;          The angle in degrees to which the torsion angle is restrained.
>            The torsion angle is the dihedral angle between the plane defined
>            by atoms 1, 2 and 3, and the plane defined by atoms 2, 3 and 4.
>;
>
>data_restr_torsion_atom_site_label_
>     loop_ _name                '_restr_torsion_atom_site_label_1'
>                                '_restr_torsion_atom_site_label_2'
>                                '_restr_torsion_atom_site_label_3'
>                                '_restr_torsion_atom_site_label_4'
>     _category                  'restr_torsion'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _list_link_parent          '_atom_site_label_'
>     _definition
>;          The _atom_site_labels of the atoms in the sequence in 
>which they are
>            linked by the bonds whose torsion angle is to be restrained.
>;
>
>data_restr_torsion_details
>     _name                      '_restr_torsion_details'
>     _category                  'restr_torsion'
>     _type                      numb
>     _list                      yes
>     _list_reference            '_restr_torsion_atom_site_label_'
>     _units                       degree
>     _definition
>;             A free text description of the restraint.
>;
>
>   data_restr_torsion_diff
>     _name                      '_restr_torsion_diff'
>     _category                  'restr_torsion'
>     _type                      numb
>     _type_conditions           su
>     _list                      yes
>     _list_reference            '_restr_torsion_atom_site_label_'
>     _units                       degree
>     _definition
>;           The difference between the target and the refined torsion angle.
>;
>
>data_restr_torsion_site_symmetry_
>     loop_ _name                '_restr_torsion_site_symmetry_1'
>                                '_restr_torsion_site_symmetry_2'
>                                '_restr_torsion_site_symmetry_3'
>                                '_restr_torsion_site_symmetry_4'
>     _category                  'restr_torsion'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_torsion_atom_site_label_'
>     _enumeration_default       '1_555'
>     loop_ _example
>           _example_detail        .     'no symmetry or translation to site'
>                                  '4'     '4th symmetry operation applied'
>                                  '7_645' '7th symm. posn.; +a on x; -b on y'
>     _definition
>;          The symmetry transformation needed to generate the coordinates
>            of the four atoms that define the torsion angle.
>
>               The symmetry code of each atom site as the symmetry-equivalent
>                position number 'n' and the cell translation number 'klm'.
>                These numbers are combined to form the code n_klm.
>                The character string n_klm is composed as follows:
>
>                n refers to the symmetry operation that is applied to the
>                coordinates stored in _atom_site_fract_x, _atom_site_fract_y
>                and _atom_site_fract_z. It should match a number given in
>                _space_group_symop_id.
>
>                k, l and m refer to the translations that are subsequently
>                applied to the symmetry-transformed coordinates to generate
>                the atom used in calculating the torsion angle. These
>                translations (x,y,z) are related to (k,l,m) by the relations
>                     k = 5 + x
>                     l = 5 + y
>                     m = 5 + z
>                By adding 5 to the translations, the use of negative numbers
>                is avoided.
>;
>
>data_restr_torsion_weight_param
>     _name                      '_restr_torsion_weight_param'
>     _category                  'restr_torsion'
>     _type                      numb
>     _list                      yes
>     _list_reference            '_restr_torsion_atom_site_label_'
>     _units                       degree
>     _enumeration_range          0:
>     _enumeration_default        0
>     _definition
>;          Weighting parameter = sqrt(1/weight).
>            It is the expectation value of the difference between
>            the refined value and the target.
>            If this parameter is set to zero, the angle will be constrained
>            to refine to the target value.
>            If this item is absent, its value will be taken as zero
>            and the distance will be constrained
>;
>
>
>
>#-------------------------------------------------------------------
># RESTRAINT 12: THE ATOMIC DISPLACEMENT PARAMETER IS RESTRAINED TO 
>BE ISOTROPIC
>#-------------------------------------------------------------------
>#
>#####################
>#                   #
>#  RESTR_U-ISO      #
>#                   #
>#####################
>
>data_restr-U-iso_[]
>     _name               	 '_restr-U-iso_[]'
>     _category                  category_overview
>     _type                      null
>     _list_reference            '_restr_U_iso_atom_site_label'
>     _definition
>;           This restraints attempts to make an anisotropic
>             atomic displaecement isotropic within the range of the
>             weighting parameter.
>             It corresponds to SHELX ISO.
>;
>loop_
>     _example
>;loop_
>   _restr_U_iso_atom_site_label
>   _restr_U_iso_weight_param
>Na1	0.003
>O3	0.008
>O8	0.008
>;
>
>data_restr_U_iso_atom_site_label
>     _name                      '_restr_U_iso_atom_site_label'
>     _category                  'restr_U_iso'
>     _type                      char
>     _list                      yes
>     _list_reference            '_restr_U_iso_atom_site_label'
>     _list_mandatory            yes
>     _list_link_parent          '_atom_site_label'
>     _definition
>; Label of the atom whose atomic displacement parameters are to be restrained.
>;
>
>data_restr_U_isotropic_weight_param
>     _name                      '_restr_U_iso_weight_param'
>     _category                  'restr_U_iso'
>     _type                      numb
>     _list                      yes
>     _list_reference            '_restr_U_iso_atom_site_label'
>     _units                     A^-2^
>     _units_detail              'reciprocal Angstrom squared'
>     _enumeration_range         0:
>     _enumeration_default       0
>     _definition
>;            The expectation value of the difference between
>              the refined and the isotropic equivalent of the
>              anisotropic atomic displacement parameters.
>              The default value of zero indicates a constraint.
>;
>
>#
># ----------------------------------------------------------------------------
># RESTRAINT 13. ADPs ARE RESTRAINED FOR A RIGID BOND.
># ----------------------------------------------------------------------------
>#  This "rigid bond" restraint restrains the anisotropic displacement
>#  parameters of two atoms so that they are equal within a certain
>#  _weight_param along the direction of the vector joining the atoms.
>#
>######################
>#                    #
>#  RESTR_U_RIGID     #
>#                    #
>######################
>#
>
>data_restr_U_rigid_[]
>     _name                     '_restr_U_rigid_[]'
>     _category                  category_overview
>     _type                      null
>     _definition
>;       The items in this category restrains the anisotropic displacement
>         parameters of two atoms to be equal within a certain
>         _weight_param along the direction of the vector joining the atoms.
>;
>     _example
>;
>loop_
>_restr_U_rigid_atom_site_label_1
>_restr_U_rigid_site_symmetry_1
>_restr_U_rigid_atom_site_label_2
>_restr_U_rigid_site_symmetry_2
>_restr_U_rigid_target_weight_param
>_restr_U_rigid_U_parallel
>_restr_U_rigid_diff
>_restr_U_rigid_details
>C1 1_555 C2 2_655 0.001 0.0023(2) 0.0006 'C1-C2 is a rigid bond'
>;
>
>data_restr_U_rigid_atom_site_label_
>     loop_ _name                '_restr_U_rigid_atom_site_label_1'
>                                '_restr_U_rigid_atom_site_label_2'
>     _category                  'restr_U_rigid'
>     _type                      char
>     _list                      yes
>     _list_mandatory            yes
>     _list_link_parent          '_atom_site_label'
>     _definition
>;       The _atom_site_labels of the two atoms that define the rigid bond.
>;
>
>data_restr_U_rigid_details
>     _name                      '_restr_U_rigid_details'
>     _category                  'restr_U_rigid'
>     _type                      char
>     _list                      yes
>     _list_reference            'restr_U_rigid_atom_site_label_'
>     _definition
>;       Free text information about the rigid bond restraint.
>;
>
>data_restr_U_rigid_diff
>     _name                      '_restr_U_rigid_diff'
>     _category                  'restr_U_rigid'
>     _type                      numb
>     _type_conditions           su
>     _list                      yes
>     _list_reference            'restr_U_rigid_atom_site_label_'
>     _units                     A^-2^
>     _units_detail              Angstrom^-2^
>     _definition
>;        The difference between the components along the bond direction
>          of the atomic displacement parameters, U, of the two atoms.
>;
>
>data_restr_U_rigid_site_symmetry_
>     loop_ _name                '_restr_U_rigid_site_symmetry_1'
>                                '_restr_U_rigid_site_symmetry_2'
>     _category                  'restr_U_rigid'
>     _type                      char
>     _list                      yes
>     _list_reference            'restr_U_rigid_atom_site_label_'
>     _enumeration_default       '1_555'
>     _definition
>;         The site symmetries of the two atoms that define the rigid bond.
>
>                The symmetry code of each atom site as the symmetry-equivalent
>                position number 'n' and the cell translation number 'klm'.
>                These numbers are combined to form the code n_klm.
>                The character string n_klm is composed as follows:
>
>                n refers to the symmetry operation that is applied to the
>                coordinates stored in _atom_site_fract_x, _atom_site_fract_y
>                and _atom_site_fract_z. It should match a number given in
>                _space_group_symop_id.
>
>                k, l and m refer to the translations that are subsequently
>                applied to the symmetry-transformed coordinates to generate
>                the atom used in calculating the rigid bond.
>                These translations (x,y,z) are related to (k,l,m)
>                by the relations
>                     k = 5 + x
>                     l = 5 + y
>                     m = 5 + z
>                By adding 5 to the translations, the use of negative numbers
>                is avoided.
>;
>     loop_ _example
>           _example_detail        .     'no symmetry or translation to site'
>                                  4     '4th symmetry operation applied'
>                                  7_645 '7th symm. posn.; +a on x; -b on y'
>
>data_restr_U_rigid_target_weight_param
>     _name                      '_restr_U_rigid_target_weight_param'
>     _category                  'restr_U_rigid'
>     _type                      numb
>     _list                      yes
>     _list_reference            'restr_U_rigid_atom_site_label_'
>     _units                     A^-2^
>     _units_detail              Angstrom^-2^
>     _enumeration_default       0
>     _definition
>;        The weighting parameter = sqrt(1/weight).
>          The expectation value of the difference between the components
>          of the atomic displacement parameter, U,
>          along the bond direction of the two atoms that define the bond.
>          This number is used to assign a weight during refinement.
>          A value of zero causes the restraint to become a constraint.
>          This item as a default value of zero.
>;
>
>data_restr_U_rigid_U_parallel
>     _name                      '_restr_U_rigid_U_parallel'
>     _category                  'restr_U_rigid'
>     _type                      numb
>     _list                      yes
>     _list_reference            'restr_U_rigid_atom_site_label_'
>     _units                     A^-2^
>     _units_detail              Angstrom^-2^
>     _enumeration_default       0
>     _definition
>;        The average value of the components parallel to the bond
>          of the atomic displacement parameters of the two atoms
>          that define the bond.
>;
>
>#
>#--------------------------------------------------------------------
># RESTRAINT 14.  TWO ATOMS ARE RESRAINED TO HAVE THE SAME ADPs
>#--------------------------------------------------------------------
>#
>#####################
>#                   #
>#  RESTR_U-SIMILAR  #
>#                   #
>#####################
>
>data_restr_U_similar_[]
>     _name                      '_restr_U_similar_[]'
>     _category                  category_overview
>     _type                      null
>     _definition
>;          This category forces the atomic displacement ellipsoids
>            of atom 2 to be equal to that of atom 1 within the range
>            of the weighting parameter.
>            This is the same as SHELX  SIMU
>;
>loop_
>_example
>;loop_
>   _restr_U_similar_atom_site_label_1
>   _restr_U_similar_atom_site_label_2
>   _restr_U_similar_weight_param
>C1	C2	0.08
>C2	C3	0.08
>;
>
>data_restr_U_similar_atom_site_label_1
>     _name                      '_restr_U_similar_atom_site_label_1'
>     _category                  'restr_U_similar'
>     _type                      char
>     _list                      yes
>   loop_
>     _list_reference            '_restr_U_similar_atom_site_label_1'
>                                '_restr_U_similar_atom_site_label_2'
>     _list_mandatory            yes
>     _list_link_parent          '_atom_site_label'
>     _definition
>;       Atom site label of first atom, the atom whose
>         atomic displacement parameters are used as the target.
>;
>
>data_restr_U_similar_atom_site_label_2
>     _name                      '_restr_U_similar_atom_site_label_2'
>     _category                  'restr_U_similar'
>     _type                      char
>     _list                      yes
>    loop_
>     _list_reference            '_restr_U_similar_atom_site_label_1'
>                                '_restr_U_similar_atom_site_label_2'
>     _list_mandatory            yes
>     _list_link_parent          '_atom_site_label'
>     _definition
>;        Atom site label of second atom, the atom whose
>          atomic displacement parameters are to be restrained
>          to be the same at atom 1.
>;
>
>data_restr_U_similar_weight_param
>     _name                      '_restr_U_similar_weight_param'
>     _category                  'restr_U_similar'
>     _type                      numb
>     _list                      yes
>   loop_
>     _list_reference            '_restr_U_similar_atom_site_label_1'
>                                '_restr_U_similar_atom_site_label_2'
>     _units                     A^-2^
>     _units_detail              'reciprocal Angstrom squared'
>     _enumeration_range         0:
>     _enumeration_default       0
>     _definition
>;         The expectation value of the difference between the
>           anisotropic atomic displacement parameters
>           of the two atoms.
>           The default value of zero represents a constraint.
>;
>
>##-------------End of Restraint and Constraint Dictionary ---------
>
>--
>T +61 (02) 9717 9907
>F +61 (02) 9717 3145
>M +61 (04) 0249 4148
>_______________________________________________
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-- 
=====================================================
  Herbert J. Bernstein, Professor of Computer Science
    Dowling College, Kramer Science Center, KSC 121
         Idle Hour Blvd, Oakdale, NY, 11769

                  +1-631-244-3035
                  yaya@dowling.edu
=====================================================
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