Crystallographic Information Framework

CIF

Expanded view
View CIF syntax

TwinCrys CIF dictionary

Version 3.1 (2016-11-15)

The DICTIONARY group defines the data items used to specify the the twinning aspects of crystals in a crystallographic study.

Category tree view of data-item definitions

TWIN
CIF 
Data items in the TWIN category record general details about
the nature of the twinning in the sample.
Terminology for twin dataname definitions was taken directly from:
"International Union of Crystallography Commission on Mathematical
and Theoretical Crystallography Research themes: Crystal twinning"
by Massimo Nespolo, February 3, 2009.
http://www.crystallography.fr/mathcryst/twins.htm .

save_TWIN

    _definition.id               TWIN
    _definition.scope            Category
    _definition.class            Set
    _definition.update           2014-06-20
    _description.text                   
;

     Data items in the TWIN category record general details about
     the nature of the twinning in the sample.
     Terminology for twin dataname definitions was taken directly from:
     "International Union of Crystallography Commission on Mathematical
     and Theoretical Crystallography Research themes: Crystal twinning"
     by Massimo Nespolo, February 3, 2009.
     http://www.crystallography.fr/mathcryst/twins.htm .
;
    _name.category_id            TWIN_GROUP
    _name.object_id              TWIN

save_
_twin.dimensionality
CIF 
The degree of overlap between the twin lattices.
Most twin lattice symmetry (TLS) and twin lattice quasi-symmetry (TLQS)
twins as defined by Donnay and Donnay will be triperiodic.

Reference: Donnay, G. & Donnay, J. D. H. (1974). Can. Mineral. 12, 422-425.

save_twin.dimensionality

    _definition.id               '_twin.dimensionality'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_dimensionality'       
    _description.text                   
;

     The degree of overlap between the twin lattices.
     Most twin lattice symmetry (TLS) and twin lattice quasi-symmetry (TLQS)
     twins as defined by Donnay and Donnay will be triperiodic.
   
     Reference: Donnay, G. & Donnay, J. D. H. (1974). Can. Mineral. 12, 422-425.
;
    _name.category_id            twin
    _name.object_id              dimensionality
    _type.purpose                State
    _type.source                 Assigned
    _type.container              Single
    _type.contents               Code
    loop_
    _enumeration_set.state
    _enumeration_set.detail
              triperiodic   'common lattice in three dimensions'     
              diperiodic    'common lattice in two dimensions'       
              monoperiodic  'common lattice in one dimension' 

save_
_twin.formation_mechanism
CIF 
A description of the method of twin formation.

save_twin.formation_mechanism

    _definition.id               '_twin.formation_mechanism'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_formation_mechanism'  
    _description.text                   
;

     A description of the method of twin formation.
;
    _name.category_id            twin
    _name.object_id              formation_mechanism
    _type.purpose                State
    _type.source                 Assigned
    _type.container              Single
    _type.contents               Code
    loop_
    _enumeration_set.state
    _enumeration_set.detail
              gt            'growth twin formed during crystal growth'         
              tt            'transformation twin formed during phase transition'        
              mt            'mechanical twin formed as a result of mechanical action'

save_
_twin.morphology
CIF 
The physical relationship of the different twins to one another.

save_twin.morphology

    _definition.id               '_twin.morphology'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_morphology'           
    _description.text                   
;

     The physical relationship of the different twins to one another.
;
    _name.category_id            twin
    _name.object_id              morphology
    _type.purpose                State
    _type.source                 Assigned
    _type.container              Single
    _type.contents               Code
    loop_
    _enumeration_set.state
    _enumeration_set.detail
              contact       'separated by a surface'       
              penetration   'sharing a volume'   
              simple        'individuals are not repeated'           
              polysynthetic  'individuals repeat in approximately linear arrangement'   
              cyclic        'individuals repeat in closed edifice' 

save_
_twin.special_details
CIF 
Information about twinning in the sample not contained in other data items.

Example:
Individuals 3 and 4 arise from form (I) following an
        enantiotropic phase transition by sudden cooling in
        a cryostat to 173K.

save_twin.special_details

    _definition.id               '_twin.special_details'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_special_details'      
    _description.text                   
;

     Information about twinning in the sample not contained in other data items.
;
    _name.category_id            twin
    _name.object_id              special_details
    _type.purpose                Describe
    _type.source                 Recorded
    _type.container              Single
    _type.contents               Text
    loop_
    _description_example.case
            
;
        Individuals 3 and 4 arise from form (I) following an
        enantiotropic phase transition by sudden cooling in
        a cryostat to 173K.
; 

save_
TWIN_INDIVIDUAL
CIF 
Data items in the TWIN_INDIVIDUAL category describe properties
of each twinned individual, and the symmetry relationships
between the individuals.

save_TWIN_INDIVIDUAL

    _definition.id               TWIN_INDIVIDUAL
    _definition.scope            Category
    _definition.class            Loop
    _definition.update           2014-06-20
    _description.text                   
;

     Data items in the TWIN_INDIVIDUAL category describe properties
     of each twinned individual, and the symmetry relationships
     between the individuals.
;
    _name.category_id            TWIN
    _name.object_id              TWIN_INDIVIDUAL
    loop_
       _category_key.name        '_twin_individual.id'

save_
_twin_individual.id
CIF 
The unique identifier for this twin individual.
The twin for which _twin_individual.twin_matrix
is the identity matrix is called the reference twin.
It is recommended that the reference twin be labelled '1'.

save_twin_individual.id

    _definition.id               '_twin_individual.id'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_individual_id'        
    _description.text                   
;

     The unique identifier for this twin individual.
     The twin for which _twin_individual.twin_matrix
     is the identity matrix is called the reference twin.
     It is recommended that the reference twin be labelled '1'.
;
    _name.category_id            twin_individual
    _name.object_id              id
    _type.purpose                Encode
    _type.source                 Assigned
    _type.container              Single
    _type.contents               Code

save_
_twin_individual.mass_fraction_refined
CIF 
The refined mass fraction of this twin individual; the sum
of all mass fractions must equal unity within the limits of
experimental uncertainty.

save_twin_individual.mass_fraction_refined

    _definition.id               '_twin_individual.mass_fraction_refined'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_individual_mass_fraction_refined'         
    _description.text                   
;

     The refined mass fraction of this twin individual; the sum
     of all mass fractions must equal unity within the limits of
     experimental uncertainty.
;
    _name.category_id            twin_individual
    _name.object_id              mass_fraction_refined
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Single
    _type.contents               Real
    _enumeration.range           0:1.0

save_
_twin_individual.twin_lattice_type
CIF 
Identification of the symmetry relationships between the
twin lattices as described in International Tables
for Crystallography (2004), Vol. C, Chapter 1.3.
The twin with the identity matrix should be denoted as 'ref'.

save_twin_individual.twin_lattice_type

    _definition.id               '_twin_individual.twin_lattice_type'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_individual_twin_lattice_type'   
    _description.text                   
;

     Identification of the symmetry relationships between the
     twin lattices as described in International Tables
     for Crystallography (2004), Vol. C, Chapter 1.3.
     The twin with the identity matrix should be denoted as 'ref'.
;
    _name.category_id            twin_individual
    _name.object_id              twin_lattice_type
    _type.purpose                State
    _type.source                 Assigned
    _type.container              Single
    _type.contents               Code
    loop_
    _enumeration_set.state
    _enumeration_set.detail
              ref           'reference twin'     
              mt_I          'merohedral class I (simple inversion)'  
              mt_II         'merohedral class II (mirror or twofold)'          
              mt_I+II       'class I and II simultaneously present'  
              rmt           'reticular merohedral'         
              pmt           'pseudo-merohedral'  
              rpmt          'reticular pseudo-merohedral'  
              nmt           'non-merohedral' 

save_
_twin_individual.twin_matrix
CIF 
The matrix U that multiplies the Miller indices h,k,l
of the reference twin to give the Miller indices h',k',l',
of the twin specified by _twin_individual_id

(h' k' l') = U (h k l )

The reference twin must have U = I, the identity matrix.

save_twin_individual.twin_matrix

    _definition.id               '_twin_individual.twin_matrix'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_individual_twin_matrix'         
    _description.text                   
;

     The matrix U that multiplies the Miller indices h,k,l
     of the reference twin to give the Miller indices h',k',l',
     of the twin specified by _twin_individual_id

                         (h' k' l') = U (h k l )

     The reference twin must have U = I, the identity matrix.
;
    _name.category_id            twin_individual
    _name.object_id              twin_matrix
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Matrix
    _type.contents               Real
    loop_
    _method.purpose
    _method.expression
     Evaluation    
;
     with t  as  twin_individual

     _twin_individual.twin_matrix =
              [[ t.twin_matrix_11, t.twin_matrix_12, t.twin_matrix_13 ],
               [ t.twin_matrix_21, t.twin_matrix_22, t.twin_matrix_23 ],
               [ t.twin_matrix_31, t.twin_matrix_32, t.twin_matrix_33 ]]
; 

save_
_twin_individual.twin_matrix_11
CIF 
The [1,1] element of the matrix U in _twin_individual.twin_matrix.

save_twin_individual.twin_matrix_11

    _definition.id               '_twin_individual.twin_matrix_11'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_individual_twin_matrix_11'      
    _description.text                   
;

     The [1,1] element of the matrix U in _twin_individual.twin_matrix.
;
    _name.category_id            twin_individual
    _name.object_id              twin_matrix_11
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Single
    _type.contents               Real

save_
_twin_individual.twin_matrix_12
CIF 
The [1,2] element of the matrix U in _twin_individual.twin_matrix.

save_twin_individual.twin_matrix_12

    _definition.id               '_twin_individual.twin_matrix_12'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_individual_twin_matrix_12'      
    _description.text                   
;

     The [1,2] element of the matrix U in _twin_individual.twin_matrix.
;
    _name.category_id            twin_individual
    _name.object_id              twin_matrix_12
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Single
    _type.contents               Real

save_
_twin_individual.twin_matrix_13
CIF 
The [1,3] element of the matrix U in _twin_individual.twin_matrix.

save_twin_individual.twin_matrix_13

    _definition.id               '_twin_individual.twin_matrix_13'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_individual_twin_matrix_13'      
    _description.text                   
;

     The [1,3] element of the matrix U in _twin_individual.twin_matrix.
;
    _name.category_id            twin_individual
    _name.object_id              twin_matrix_13
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Single
    _type.contents               Real

save_
_twin_individual.twin_matrix_21
CIF 
The [2,1] element of the matrix U in _twin_individual.twin_matrix.

save_twin_individual.twin_matrix_21

    _definition.id               '_twin_individual.twin_matrix_21'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_individual_twin_matrix_21'      
    _description.text                   
;

     The [2,1] element of the matrix U in _twin_individual.twin_matrix.
;
    _name.category_id            twin_individual
    _name.object_id              twin_matrix_21
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Single
    _type.contents               Real

save_
_twin_individual.twin_matrix_22
CIF 
The [2,2] element of the matrix U in _twin_individual.twin_matrix.

save_twin_individual.twin_matrix_22

    _definition.id               '_twin_individual.twin_matrix_22'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_individual_twin_matrix_22'      
    _description.text                   
;

     The [2,2] element of the matrix U in _twin_individual.twin_matrix.
;
    _name.category_id            twin_individual
    _name.object_id              twin_matrix_22
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Single
    _type.contents               Real

save_
_twin_individual.twin_matrix_23
CIF 
The [3,2] element of the matrix U in _twin_individual.twin_matrix.

save_twin_individual.twin_matrix_23

    _definition.id               '_twin_individual.twin_matrix_23'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_individual_twin_matrix_23'      
    _description.text                   
;

     The [3,2] element of the matrix U in _twin_individual.twin_matrix.
;
    _name.category_id            twin_individual
    _name.object_id              twin_matrix_23
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Single
    _type.contents               Real

save_
_twin_individual.twin_matrix_31
CIF 
The [1,3] element of the matrix U in _twin_individual.twin_matrix.

save_twin_individual.twin_matrix_31

    _definition.id               '_twin_individual.twin_matrix_31'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_individual_twin_matrix_31'      
    _description.text                   
;

     The [1,3] element of the matrix U in _twin_individual.twin_matrix.
;
    _name.category_id            twin_individual
    _name.object_id              twin_matrix_31
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Single
    _type.contents               Real

save_
_twin_individual.twin_matrix_32
CIF 
The [2,3] element of the matrix U in _twin_individual.twin_matrix.

save_twin_individual.twin_matrix_32

    _definition.id               '_twin_individual.twin_matrix_32'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_individual_twin_matrix_32'      
    _description.text                   
;

     The [2,3] element of the matrix U in _twin_individual.twin_matrix.
;
    _name.category_id            twin_individual
    _name.object_id              twin_matrix_32
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Single
    _type.contents               Real

save_
_twin_individual.twin_matrix_33
CIF 
The [3,3] element of the matrix U in _twin_individual.twin_matrix.

save_twin_individual.twin_matrix_33

    _definition.id               '_twin_individual.twin_matrix_33'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_individual_twin_matrix_33'      
    _description.text                   
;

     The [3,3] element of the matrix U in _twin_individual.twin_matrix.
;
    _name.category_id            twin_individual
    _name.object_id              twin_matrix_33
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Single
    _type.contents               Real

save_
TWIN_REFLN
CIF 
Items in the TWIN_REFLN category tabulate the calculated values of F^2^
for each peak observed in the diffraction pattern, together with the
measured value of F^2^.  The calculated F^2^ for an observed peak is
a weighted sum of the contribution of all the twin components.  The
calculated structure factor for each twin contribution can also be given.

save_TWIN_REFLN

    _definition.id               TWIN_REFLN
    _definition.scope            Category
    _definition.class            Loop
    _definition.update           2014-06-20
    _description.text                   
;

     Items in the TWIN_REFLN category tabulate the calculated values of F^2^
     for each peak observed in the diffraction pattern, together with the 
     measured value of F^2^.  The calculated F^2^ for an observed peak is 
     a weighted sum of the contribution of all the twin components.  The 
     calculated structure factor for each twin contribution can also be given.
;
    _name.category_id            TWIN
    _name.object_id              TWIN_REFLN
    loop_
       _category_key.name
           '_twin_refln.datum_id'  '_twin_refln.individual_id'

save_
_twin_refln.datum_id
CIF 
This item serves to identify an observed diffraction peak.
It may include contributions from one or more twin components
and so may appear more than once in the list.
The values of _twin_refln.F_squared_calc and
_twin_refln.F_squared_meas indexed by _twin_refln.datum_id
include the contributions from all the twins.
The diffraction peak is indexed by _twin_refln.index_hkl
referred to the cell of the twin component identified by
_twin_refln.individual_id.

save_twin_refln.datum_id

    _definition.id               '_twin_refln.datum_id'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_refln_datum_id'       
    _description.text                   
;

     This item serves to identify an observed diffraction peak.
     It may include contributions from one or more twin components
     and so may appear more than once in the list.
     The values of _twin_refln.F_squared_calc and
     _twin_refln.F_squared_meas indexed by _twin_refln.datum_id 
     include the contributions from all the twins.
     The diffraction peak is indexed by _twin_refln.index_hkl 
     referred to the cell of the twin component identified by 
     _twin_refln.individual_id.
;
    _name.category_id            twin_refln
    _name.object_id              datum_id
    _type.purpose                Key
    _type.source                 Assigned
    _type.container              Single
    _type.contents               Code

save_
_twin_refln.F_squared_calc
CIF 
Calculated value for the overall squared structure factors (in
electrons squared for X-ray diffraction) arising from all
the twin contributions to the peak defined by _twin_refln_datum_id.
The total contribution from all twins to a single observed
reflection is modelled according to the method of Pratt, Coyle
and Ibers as follows:

_twin_refln.F_squared_calc = osf * Sum (mf * _reflnr._F_squared_calc)

where osf is the overall scale factor,
mf is the mass fraction,
and the sum is taken over all the twin components that contribute
to this diffraction peak.

Reference: Pratt, C. S., Coyle, B. A. & Ibers, J. A. (1971).
J. Chem. Soc. A, pp. 2146-2151.

save_twin_refln.F_squared_calc

    _definition.id               '_twin_refln.F_squared_calc'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_refln_F_squared_calc'           
    _description.text                   
;

     Calculated value for the overall squared structure factors (in
     electrons squared for X-ray diffraction) arising from all
     the twin contributions to the peak defined by _twin_refln_datum_id.
     The total contribution from all twins to a single observed
     reflection is modelled according to the method of Pratt, Coyle
     and Ibers as follows:

     _twin_refln.F_squared_calc = osf * Sum (mf * _reflnr._F_squared_calc)

     where osf is the overall scale factor,
     mf is the mass fraction,
     and the sum is taken over all the twin components that contribute
     to this diffraction peak.

     Reference: Pratt, C. S., Coyle, B. A. & Ibers, J. A. (1971).
     J. Chem. Soc. A, pp. 2146-2151.
;
    _name.category_id            twin_refln
    _name.object_id              F_squared_calc
    _type.purpose                Measurand
    _type.source                 Derived
    _type.container              Single
    _type.contents               Real

save_
_twin_refln.F_squared_calc_individual
CIF 
Contribution of the twin identified by _twin_refln.individual_id
to _twin_refln.F_squared_calc.

_twin_refln.F_squared_calc_individual = osf * mf * _refln.F_squared_calc

where osf is the overall scale factor, mf is the mass factor.
For X-ray diffraction the units are electrons squared.

save_twin_refln.F_squared_calc_individual

    _definition.id               '_twin_refln.F_squared_calc_individual'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_refln_F_squared_calc_individual'          
    _description.text                   
;

     Contribution of the twin identified by _twin_refln.individual_id
     to _twin_refln.F_squared_calc.

     _twin_refln.F_squared_calc_individual = osf * mf * _refln.F_squared_calc

     where osf is the overall scale factor, mf is the mass factor.
     For X-ray diffraction the units are electrons squared.
;
    _name.category_id            twin_refln
    _name.object_id              F_squared_calc_individual
    _type.purpose                Measurand
    _type.source                 Derived
    _type.container              Single
    _type.contents               Real

save_
_twin_refln.F_squared_meas
CIF 
The observed value F^2^ of the peak referenced by
_twin_refln.datum_id. This is typically the observed peak
intensity after Lorentz and polarization corrections.

save_twin_refln.F_squared_meas

    _definition.id               '_twin_refln.F_squared_meas'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_refln_F_squared_meas'           
    _description.text                   
;

     The observed value F^2^ of the peak referenced by
     _twin_refln.datum_id. This is typically the observed peak
     intensity after Lorentz and polarization corrections.
;
    _name.category_id            twin_refln
    _name.object_id              F_squared_meas
    _type.purpose                Measurand
    _type.source                 Derived
    _type.container              Single
    _type.contents               Real

save_
_twin_refln.F_squared_meas_sigma
CIF 
Standard uncertainty of _twin_refln_F_squared_meas

save_twin_refln.F_squared_meas_sigma

    _definition.id               '_twin_refln.F_squared_meas_sigma'
    _definition.update           2014-07-30
    loop_
      _alias.definition_id
          '_twin_refln_F_squared_meas_sigma'     
          '_twin_refln_F_squared_sigma'          
          '_twin_refln.F_squared_sigma'          
          '_twin_refln.F_squared_meas_su' 
    _description.text                   
;

     Standard uncertainty of _twin_refln_F_squared_meas
;
    _name.category_id            twin_refln
    _name.object_id              F_squared_meas_su
    _name.linked_item_id         '_twin_refln.F_squared_meas'
    _type.purpose                SU
    _type.source                 Related
    _type.container              Single
    _type.contents               Real

save_
_twin_refln.include_status
CIF 
A symbol indicating how the reflection is treated during refinement.

save_twin_refln.include_status

    _definition.id               '_twin_refln.include_status'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_refln_include_status'           
    _description.text                   
;

     A symbol indicating how the reflection is treated during refinement.
;
    _name.category_id            twin_refln
    _name.object_id              include_status
    _type.purpose                State
    _type.source                 Assigned
    _type.container              Single
    _type.contents               Code
    loop_
    _enumeration_set.state
    _enumeration_set.detail
              o             
;            (lower-case letter o for 'observed') satisfies _refine_ls.d_res_high
             satisfies _refine_ls.d_res_low exceeds _reflns.threshold_expression
;        
              <;             
;               satisfies _refine_ls.d_res_high satisfies _refine_ls.d_res_low
                does not exceed _reflns.threshold_expression
;        
              -             'systematically absent reflection'       
              x             'unreliable measurement -- not used'     
              r             'removed from the refinement for other reasons'    
              h             'does not satisfy _refine_ls_d_res_high'           
              l             'does not satisfy _refine_ls_d_res_low' 
    _enumeration.default         o

save_
_twin_refln.index_h
CIF 
Miller index h in the vector _twin_refln.index_hkl.

save_twin_refln.index_h

    _definition.id               '_twin_refln.index_h'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_refln_index_h'        
    _description.text                   
;

     Miller index h in the vector _twin_refln.index_hkl.
;
    _name.category_id            twin_refln
    _name.object_id              index_h
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Single
    _type.contents               Integer

save_
_twin_refln.index_hkl
CIF 
Miller index vector of a reflection for the twin component
labelled by _twin_refln.individual_id.
The values of the Miller indices must correspond
to the cell defined for this twin component.

save_twin_refln.index_hkl

    _definition.id               '_twin_refln.index_hkl'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_refln_index_hkl'      
    _description.text                   
;

     Miller index vector of a reflection for the twin component
     labelled by _twin_refln.individual_id.
     The values of the Miller indices must correspond
     to the cell defined for this twin component.
;
    _name.category_id            twin_refln
    _name.object_id              index_hkl
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Matrix
    _type.contents               Integer
    _type.dimension              '[3]'
    loop_
    _method.purpose
    _method.expression
     Evaluation    
;
     With t as twin_refln

       _twin_refln.index_hkl =  [t.index_h, t.index_k, t.index_l]
; 

save_
_twin_refln.index_k
CIF 
Miller index k in the vector _twin_refln.index_hkl.

save_twin_refln.index_k

    _definition.id               '_twin_refln.index_k'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_refln_index_k'        
    _description.text                   
;

     Miller index k in the vector _twin_refln.index_hkl. 
;
    _name.category_id            twin_refln
    _name.object_id              index_k
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Single
    _type.contents               Integer

save_
_twin_refln.index_l
CIF 
Miller index l in the vector _twin_refln.index_hkl.

save_twin_refln.index_l

    _definition.id               '_twin_refln.index_l'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_refln_index_l'        
    _description.text                   
;

     Miller index l in the vector _twin_refln.index_hkl. 
;
    _name.category_id            twin_refln
    _name.object_id              index_l
    _type.purpose                Number
    _type.source                 Derived
    _type.container              Single
    _type.contents               Integer

save_
_twin_refln.individual_id
CIF 
The unique identifier of the twin individual
whose Miller indices are given in _twin_refln_index_hkl.
The ID must match a _twin.individual_id in the
TWIN_INDIVIDUAL category.

The list reference includes both _twin_refln.datum_id and
_twin_refln.individual_id.  The combination of these two items
may only appear once in a list.

save_twin_refln.individual_id

    _definition.id               '_twin_refln.individual_id'
    _definition.update           2014-06-20
    loop_
      _alias.definition_id
          '_twin_refln_individual_id'  
    _description.text                   
;

     The unique identifier of the twin individual
     whose Miller indices are given in _twin_refln_index_hkl.
     The ID must match a _twin.individual_id in the
     TWIN_INDIVIDUAL category.

     The list reference includes both _twin_refln.datum_id and
     _twin_refln.individual_id.  The combination of these two items
     may only appear once in a list.
;
    _name.category_id            twin_refln
    _name.object_id              individual_id
    _name.linked_item_id         '_twin.individual_id'
    _type.purpose                Encode
    _type.source                 Assigned
    _type.container              Single
    _type.contents               Code

save_

Revision history

International Tables for Crystallography

Volume G: Definition and exchange of crystallographic data

First online edition (2006)

Edited by S. R. Hall and B. McMahon

An essential guide and reference to CIF for programmers, data managers handling crystal-structure information and practising crystallographers.