CIF dictionary browser

CIF

Expanded view
View CIF syntax

cif_pd.dic CIF dictionary

Category view of data-item definitions

_PD_BLOCK_[PD]

CIF

_pd_block_id is used to assign a unique ID code to a data block.

This code is then used for references between different blocks
(see _pd_block_diffractogram_id, _pd_calib_std_external_block_id
and _pd_phase_block_id).

Note that a data block may contain only a single diffraction
data set or information about a single crystalline phase.
However, a single diffraction measurement may yield structural
information on more than one phase, or a single structure
determination may use more than one data set. Alternatively,
results from a single data set, such as calibration parameters
from measurements of a standard, may be used for many subsequent
analyses. Through use of the ID code, a reference made between
data sets may be preserved when the file is exported from the
laboratory from which the CIF originated.

The ID code assigned to each data block should be unique with
respect to an ID code assigned for any other data block in the
world. The naming scheme chosen for the block-ID format is
designed to ensure uniqueness.

It is the responsibility of a data archive site or local
laboratory to create a catalogue of block ID's if that site
wishes to resolve these references.

data_pd_block_[pd]
    _name                       '_pd_block_[pd]'
    _category                     category_overview
    _type                         null
    _definition
;              _pd_block_id is used to assign a unique ID code to a data block.
               This code is then used for references between different blocks
               (see _pd_block_diffractogram_id, _pd_calib_std_external_block_id
               and _pd_phase_block_id).

               Note that a data block may contain only a single diffraction
               data set or information about a single crystalline phase. 
               However, a single diffraction measurement may yield structural 
               information on more than one phase, or a single structure 
               determination may use more than one data set. Alternatively, 
               results from a single data set, such as calibration parameters 
               from measurements of a standard, may be used for many subsequent 
               analyses. Through use of the ID code, a reference made between 
               data sets may be preserved when the file is exported from the 
               laboratory from which the CIF originated.

               The ID code assigned to each data block should be unique with
               respect to an ID code assigned for any other data block in the
               world. The naming scheme chosen for the block-ID format is
               designed to ensure uniqueness.

               It is the responsibility of a data archive site or local
               laboratory to create a catalogue of block ID's if that site
               wishes to resolve these references.
;

_pd_block_id

CIF

Used to assign a unique character string to a block.

Note that this code is not intended to be parsed; the
concatenation of several strings is used in order to
generate a string that can reasonably be expected to
be unique.

This code is assigned by the originator of the data set and
is used for references between different CIF blocks.
The ID will normally be created when the block is first
created. It is possible to loop more than one ID for a
block: if changes or additions are made to the
block later, a new ID may be assigned, but the original name
should be retained.

The format for the ID code is:
  <date-time>|<block_name>|<creator_name>|<instr_name>

 <date-time>    is the date and time the CIF was created
                or modified.

 <block_name>   is an arbitrary name assigned by the
                originator of the data set. It will
                usually match the name of the phase
                and possibly the name of the current CIF
                data block (i.e. the string xxxx in a
                data_xxxx identifier). It may be a sample name.

 <creator_name> is the name of the person who measured the
                diffractogram, or prepared or modified the CIF.

 <instr_name>  is a unique name (as far as possible) for
                the data-collection instrument, preferably
                containing the instrument serial number for
                commercial instruments. It is also possible to
                use the Internet name or address for the
                instrument computer as a unique name.

As blocks are created in a CIF, the original sample identifier
(i.e. <block_name>) should be retained, but the <creator_name>
may be changed and the <date-time> will always change.
The <date-time> will usually match either the
_pd_meas_datetime_initiated or the _pd_proc_info_datetime
entry.

Within each section of the code, the following characters
may be used:
              A-Z a-z 0-9 # & * . : , - _ + / ( ) \ [ ]

The sections are separated with vertical rules '|' which are
not allowed within the sections. Blank spaces may also
not be used.  Capitalization may be used within the ID code
but should not be considered significant - searches for
data-set ID names should be case-insensitive.

Date-time entries are in the standard CIF format
'yyyy-mm-ddThh:mm:ss+zz' Use of seconds and a time zone
is optional, but use of hours and minutes is strongly
encouraged as this will help ensure that the ID code is unique.

An archive site that wishes to make CIFs available via
the web may substitute the URL for the file containing the
appropriate block for the final two sections of the ID
(<creator_name> and <instr_name>). Note that this should
not be done unless the archive site is prepared to keep the
file available online indefinitely.

Examples:

1991-15-09T16:54|Si-std|B.Toby|D500#1234-987

1991-15-09T16:54|SEPD7234|B.Toby|SEPD.IPNS.ANL.GOV

data_pd_block_id
    _name                      '_pd_block_id'
    _category                    pd_block
    _type                        char
    _list                        both
    loop_ _example
                         1991-15-09T16:54|Si-std|B.Toby|D500#1234-987
                         1991-15-09T16:54|SEPD7234|B.Toby|SEPD.IPNS.ANL.GOV
    _definition
;              Used to assign a unique character string to a block.
               Note that this code is not intended to be parsed; the
               concatenation of several strings is used in order to
               generate a string that can reasonably be expected to
               be unique.

               This code is assigned by the originator of the data set and
               is used for references between different CIF blocks.
               The ID will normally be created when the block is first
               created. It is possible to loop more than one ID for a
               block: if changes or additions are made to the
               block later, a new ID may be assigned, but the original name
               should be retained.

               The format for the ID code is:
                 <date-time>|<block_name>|<creator_name>|<instr_name>

                <date-time>    is the date and time the CIF was created
                               or modified.

                <block_name>   is an arbitrary name assigned by the
                               originator of the data set. It will
                               usually match the name of the phase
                               and possibly the name of the current CIF
                               data block (i.e. the string xxxx in a
                               data_xxxx identifier). It may be a sample name.

                <creator_name> is the name of the person who measured the
                               diffractogram, or prepared or modified the CIF.

                <instr_name>  is a unique name (as far as possible) for
                               the data-collection instrument, preferably
                               containing the instrument serial number for
                               commercial instruments. It is also possible to
                               use the Internet name or address for the
                               instrument computer as a unique name.

               As blocks are created in a CIF, the original sample identifier
               (i.e. <block_name>) should be retained, but the <creator_name>
               may be changed and the <date-time> will always change.
               The <date-time> will usually match either the
               _pd_meas_datetime_initiated or the _pd_proc_info_datetime
               entry.

               Within each section of the code, the following characters
               may be used:
                             A-Z a-z 0-9 # & * . : , - _ + / ( ) \ [ ]

               The sections are separated with vertical rules '|' which are
               not allowed within the sections. Blank spaces may also
               not be used.  Capitalization may be used within the ID code
               but should not be considered significant - searches for
               data-set ID names should be case-insensitive.

               Date-time entries are in the standard CIF format
               'yyyy-mm-ddThh:mm:ss+zz' Use of seconds and a time zone
               is optional, but use of hours and minutes is strongly
               encouraged as this will help ensure that the ID code is unique.

               An archive site that wishes to make CIFs available via
               the web may substitute the URL for the file containing the
               appropriate block for the final two sections of the ID
               (<creator_name> and <instr_name>). Note that this should
               not be done unless the archive site is prepared to keep the
               file available online indefinitely.
;

#......................... Measured Diffractogram Information

_PD_CALC_[PD]

CIF

This section is used for storing a computed diffractogram trace.

This may be a simulated powder pattern for a material from a
program such as LAZY/PULVERIX or the computed intensities from a
Rietveld refinement.

data_pd_calc_[pd]
    _name                       '_pd_calc_[pd]'
    _category                     category_overview
    _type                         null

    _definition
;              This section is used for storing a computed diffractogram trace.
               This may be a simulated powder pattern for a material from a
               program such as LAZY/PULVERIX or the computed intensities from a
               Rietveld refinement.
;

_pd_calc_method

CIF

A description of the method used for the calculation of

the intensities in _pd_calc_intensity_. If the pattern was
calculated from crystal structure data, the atom coordinates
and other crystallographic information should be included
using the core CIF _atom_site_ and _cell_ data items.

data_pd_calc_method
    _name                      '_pd_calc_method'
    _category                    pd_calc
    _type                        char
    _definition
;              A description of the method used for the calculation of
               the intensities in _pd_calc_intensity_. If the pattern was
               calculated from crystal structure data, the atom coordinates
               and other crystallographic information should be included
               using the core CIF _atom_site_ and _cell_ data items.
;


#......................... Peak Table

_PD_CALIB_[PD]

CIF

This section defines the parameters used for the calibration

of the instrument that are used directly or indirectly in the
interpretation of this data set. The information in this
section of the CIF should generally be written when the
intensities are first measured, but from then on should remain
unchanged. Loops may be used for calibration information that
differs by detector channel. The _pd_calibration_ items,
however, are never looped.

Examples:

_pd_calib_std_external_block_id
               QuartzPlate|D500#1234-987|B.Toby|91-15-09|14:02
   _pd_calib_std_external_name
               'Arkansas Stone quartz plate'

_pd_calibration_conversion_eqn
    ; 2~actual~ = 2~setting~ + arctan(
      cos(P~1~)/{1/[P~0~ (CC - CH~0~ - P~2~ CC^2^)] - sin(P~1~)})
    ;

data_pd_calib_[pd]
    _name                       '_pd_calib_[pd]'
    _category                     category_overview
    _type                         null
    loop_
        _example
        _example_detail
#----------------------------------------------------------------------------
;
   _pd_calib_std_external_block_id
               QuartzPlate|D500#1234-987|B.Toby|91-15-09|14:02
   _pd_calib_std_external_name
               'Arkansas Stone quartz plate'
;
;
    Example 1.
;
;
    _pd_calibration_conversion_eqn
    ; 2\q~actual~ = 2\q~setting~ + arctan(
      cos(P~1~)/{1/[P~0~ (CC - CH~0~ - P~2~ CC^2^)] - sin(P~1~)})
    ;
;
;
    Example 2 - 
                2\q~actual~ = 2\q~setting~ + arctan( cos(P~1~) / {1/[P~0~
                  (CC - CH~0~ - P~2~ CC^2^)] - sin(P~1~)} ).

                This allows for the calibration of 2\q for a linear
                position-sensitive detector (PSD) where the PSD has been
                set so that the 'centre channel' (CH~0~) is located at
                2\q~setting~ as a function of the channel number (CC). In
                addition to CH~0~, variables P~0~, P~1~ and P~2~ are
                calibration constants, where P~0~ is the width of a PSD
                channel in degrees, P~1~ is the angle of the PSD with respect
                to the perpendicular and P~2~ is a quadratic term for
                nonlinearities in the detector.
;
#----------------------------------------------------------------------------
    _definition
;              This section defines the parameters used for the calibration 
               of the instrument that are used directly or indirectly in the 
               interpretation of this data set. The information in this 
               section of the CIF should generally be written when the 
               intensities are first measured, but from then on should remain 
               unchanged. Loops may be used for calibration information that 
               differs by detector channel. The _pd_calibration_ items, 
               however, are never looped.
;

_pd_calib_2theta

CIF

Data names:
_pd_calib_2theta_offset
_pd_calib_2theta_off_point
_pd_calib_2theta_off_min
_pd_calib_2theta_off_max

_pd_calib_2theta_offset defines an offset angle (in degrees)

used to calibrate 2 (as defined in _pd_meas_2theta_).
Calibration is done by adding the offset:

     2~calibrated~ = 2~measured~ + 2~offset~

For cases where the _pd_calib_2theta_offset value is
not a constant, but rather varies with 2, a set
of offset values can be supplied in a loop. In this case,
the value where the offset has been determined can be
specified as _pd_calib_2theta_off_point. Alternatively, a
range where the offset is applicable can be specified using
_pd_calib_2theta_off_min and _pd_calib_2theta_off_max.

data_pd_calib_2theta_
    loop_ _name                '_pd_calib_2theta_offset'
                               '_pd_calib_2theta_off_point'
                               '_pd_calib_2theta_off_min'
                               '_pd_calib_2theta_off_max'
    _category                    pd_calib
    _type                        numb
    _list                        both
    _list_reference            '_pd_calib_detector_id'
    _units                       deg
    _units_detail               'degrees'
    _enumeration_range           -180.0:180.0
    _definition
;              _pd_calib_2theta_offset defines an offset angle (in degrees)
               used to calibrate 2\q (as defined in _pd_meas_2theta_).
               Calibration is done by adding the offset:

                    2\q~calibrated~ = 2\q~measured~ + 2\q~offset~

               For cases where the _pd_calib_2theta_offset value is
               not a constant, but rather varies with 2\q, a set
               of offset values can be supplied in a loop. In this case,
               the value where the offset has been determined can be
               specified as _pd_calib_2theta_off_point. Alternatively, a
               range where the offset is applicable can be specified using
               _pd_calib_2theta_off_min and _pd_calib_2theta_off_max.
;

_pd_calib_detector_id

CIF

A code which identifies the detector or channel number in a

position-sensitive, energy-dispersive or other multiple-detector
instrument. Note that this code should match the code name used
for _pd_meas_detector_id.

data_pd_calib_detector_id
    _name                      '_pd_calib_detector_id'
    _category                    pd_calib
    _type                        char
    _list                        yes
    _list_mandatory              yes
    _list_link_child           '_pd_meas_detector_id'
    _definition
;              A code which identifies the detector or channel number in a
               position-sensitive, energy-dispersive or other multiple-detector
               instrument. Note that this code should match the code name used
               for _pd_meas_detector_id.
;

_pd_calib_detector_response

CIF

A value that indicates the relative sensitivity of each

detector. This can compensate for differences in electronics,
size and collimation. Usually, one detector or the mean for
all detectors will be assigned the value of 1.

data_pd_calib_detector_response
    _name                      '_pd_calib_detector_response'
    _category                    pd_calib
    _type                        numb
    _list                        yes
    _list_reference            '_pd_calib_detector_id'
    _enumeration_range           0.0:
    _definition
;              A value that indicates the relative sensitivity of each
               detector. This can compensate for differences in electronics,
               size and collimation. Usually, one detector or the mean for
               all detectors will be assigned the value of 1.
;

_pd_calib_std_external

CIF

Data names:
_pd_calib_std_external_block_id
_pd_calib_std_external_name

Identifies the data set used as an external standard for

the diffraction angle or the intensity calibrations.
*_name specifies the name of the material and
*_id the _pd_block_id for the CIF containing calibration
measurements. If more than one data set is used for
calibration, these fields may be looped.

data_pd_calib_std_external_
    loop_ _name                '_pd_calib_std_external_block_id'
                               '_pd_calib_std_external_name'
    _category                    pd_calib
    _type                        char
    _list                        both
    _list_reference            '_pd_calib_detector_id'
    _definition
;              Identifies the data set used as an external standard for
               the diffraction angle or the intensity calibrations.
               *_name specifies the name of the material and
               *_id the _pd_block_id for the CIF containing calibration
               measurements. If more than one data set is used for
               calibration, these fields may be looped.
;

_pd_calib_std_internal_mass_%

CIF

Per cent presence of the internal standard specified by the

data item _pd_calib_std_internal_name expressed as 100 times
the ratio of the amount of standard added to the original
sample mass.

data_pd_calib_std_internal_mass_%
    _name                      '_pd_calib_std_internal_mass_%'
    _category                    pd_calib
    _type                        numb
    _type_conditions             esd
    _list                        both
    _list_reference            '_pd_calib_detector_id'
    _enumeration_range           0.0:100.0
    _definition
;              Per cent presence of the internal standard specified by the
               data item _pd_calib_std_internal_name expressed as 100 times
               the ratio of the amount of standard added to the original
               sample mass.
;

_pd_calib_std_internal_name

CIF

Identity of material(s) used as an internal intensity standard.

Examples:

NIST 640a Silicon standard

Al2O3

data_pd_calib_std_internal_name
    _name                      '_pd_calib_std_internal_name'
    _category                    pd_calib
    _type                        char
    _list                        both
    _list_reference            '_pd_calib_detector_id'
    loop_ _example              'NIST 640a Silicon standard'
                                'Al2O3'
    _definition
;              Identity of material(s) used as an internal intensity standard.
;

_PD_CHAR_[PD]

CIF

This section contains experimental (non-diffraction) information

relevant to the chemical and physical nature of the material.

data_pd_char_[pd]
    _name                       '_pd_char_[pd]'
    _category                     category_overview
    _type                         null
    _definition
;   This section contains experimental (non-diffraction) information
    relevant to the chemical and physical nature of the material.
;

_pd_char_atten_coef_mu

CIF

Data names:
_pd_char_atten_coef_mu_obs
_pd_char_atten_coef_mu_calc

The observed and calculated linear attenuation coefficient,

, in units of inverse millimetres. Note that this quantity
is sometimes referred to as the mass absorption coefficient;
however, this term accounts for other potentially significant
losses of incident radiation, for example incoherent
scattering of neutrons.

The calculated  will be obtained from the atomic content of
the cell, the average density (allowing for specimen packing)
and the radiation wavelength. The observed  will be
determined by a transmission measurement.
Note that _pd_char_atten_coef_mu_calc will differ from
_exptl_absorpt_coefficient_mu if the packing density is
not unity.

data_pd_char_atten_coef_mu_
    loop_ _name                '_pd_char_atten_coef_mu_obs'
                               '_pd_char_atten_coef_mu_calc'
    _category                    pd_char
    _type                        numb
    _enumeration_range           0.0:
    _units                       mm^-1^
    _units_detail                'reciprocal millimetres'
    _definition
;              The observed and calculated linear attenuation coefficient,
               \m, in units of inverse millimetres. Note that this quantity
               is sometimes referred to as the mass absorption coefficient;
               however, this term accounts for other potentially significant
               losses of incident radiation, for example incoherent
               scattering of neutrons.

               The calculated \m will be obtained from the atomic content of
               the cell, the average density (allowing for specimen packing)
               and the radiation wavelength. The observed \m will be
               determined by a transmission measurement.
               Note that _pd_char_atten_coef_mu_calc will differ from
               _exptl_absorpt_coefficient_mu if the packing density is
               not unity.
;

_pd_char_colour

CIF

The colour of the material used for the measurement.

To facilitate more standardized use of names, the
following guidelines for colour naming developed by
Peter Bayliss for the International Centre for
Diffraction Data (ICDD) should be followed. Note that
combinations of descriptors are separated by an
underscore.

Allowed colours are:
  colourless, white, black, gray, brown, red, pink,
  orange, yellow, green, blue, violet.

Colours may be modified using prefixes of:
  light, dark, whitish, blackish, grayish, brownish,
  reddish, pinkish, orangish, yellowish, greenish, bluish.

Intermediate hues may be indicated with two colours:
e.g. blue_green or bluish_green.

For metallic materials, the term metallic may be added:
e.g. reddish_orange_metallic for copper.

The ICDD standard allows commas to be used for minerals
that occur with ranges of colours; however this usage is
not appropriate for the description of a single sample.

Examples:

dark_green

orange_red

brownish_red

yellow_metallic

data_pd_char_colour
    _name                      '_pd_char_colour'
    _category                    pd_char
    _type                        char
    loop_ _example               dark_green
                                 orange_red
                                 brownish_red
                                 yellow_metallic
    _definition
;              The colour of the material used for the measurement.
               To facilitate more standardized use of names, the
               following guidelines for colour naming developed by
               Peter Bayliss for the International Centre for 
               Diffraction Data (ICDD) should be followed. Note that
               combinations of descriptors are separated by an
               underscore.

               Allowed colours are:
                 colourless, white, black, gray, brown, red, pink,
                 orange, yellow, green, blue, violet.

               Colours may be modified using prefixes of:
                 light, dark, whitish, blackish, grayish, brownish,
                 reddish, pinkish, orangish, yellowish, greenish, bluish.

               Intermediate hues may be indicated with two colours:
               e.g. blue_green or bluish_green.

               For metallic materials, the term metallic may be added:
               e.g. reddish_orange_metallic for copper.

               The ICDD standard allows commas to be used for minerals
               that occur with ranges of colours; however this usage is
               not appropriate for the description of a single sample.
;

_pd_char_particle_morphology

CIF

A description of the sample morphology and estimates for

particle sizes (before grinding/sieving, if noted by
_pd_spec_preparation). Include the method used for
these estimates (SEM, visual estimate etc.).

data_pd_char_particle_morphology
    _name                      '_pd_char_particle_morphology'
    _category                    pd_char
    _type                        char
    _definition
;              A description of the sample morphology and estimates for
               particle sizes (before grinding/sieving, if noted by
               _pd_spec_preparation). Include the method used for
               these estimates (SEM, visual estimate etc.).
;

_pd_char_special_details

CIF

Additional characterization information relevant to the sample

or documentation of non-routine processing steps used
for characterization.

data_pd_char_special_details
    _name                      '_pd_char_special_details'
    _category                    pd_char
    _type                        char
    _definition
;              Additional characterization information relevant to the sample
               or documentation of non-routine processing steps used
               for characterization.
;

#............................. Data Tabulation and Book-keeping Across Tables

_PD_MEAS_[PD]

CIF

This section contains the measured diffractogram and information

about the conditions used for the measurement of the diffraction
data set, prior to processing and application of correction
terms. While additional information may be added to the CIF
as data are processed and transported between laboratories
(possibly with the addition of a new _pd_block_id entry), the
information in this section of the CIF will rarely be changed
once data collection is complete.

Where possible, measurements in this section should have no
post-collection processing applied (normalizations, corrections,
smoothing, zero-offset corrections etc.). Such corrected
measurements should be recorded in the _pd_proc_ section.

Data sets that are measured as counts, where a standard
uncertainty can be considered equivalent to the standard
deviation and where the standard deviation can be estimated
as the square root of the number of counts recorded, should
use the _pd_meas_counts_ fields. All other intensity values
should be recorded using _pd_meas_intensity_.

Example:

_pd_meas_info_author_name        'Cranswick, Lachlan'
    _pd_meas_info_author_email       [email protected]
    _pd_meas_info_author_address     ?
    _pd_meas_datetime_initiated      1992-03-23T17:20

    _pd_meas_scan_method             step
    _pd_meas_2theta_range_min        6.0
    _pd_meas_2theta_range_max        164.0
    _pd_meas_2theta_range_inc        0.025
    _pd_meas_step_count_time         2.0

data_pd_meas_[pd]
    _name                     '_pd_meas_[pd]'
    _category                   category_overview
    _type                       null
    loop_
        _example
        _example_detail
#----------------------------------------------------------------------------
;
    _pd_meas_info_author_name        'Cranswick, Lachlan'
    _pd_meas_info_author_email       [email protected]
    _pd_meas_info_author_address     ?
    _pd_meas_datetime_initiated      1992-03-23T17:20

    _pd_meas_scan_method             step
    _pd_meas_2theta_range_min        6.0
    _pd_meas_2theta_range_max        164.0
    _pd_meas_2theta_range_inc        0.025
    _pd_meas_step_count_time         2.0
;
;
    Example 1.
;
#----------------------------------------------------------------------------
    _definition
;              This section contains the measured diffractogram and information
               about the conditions used for the measurement of the diffraction 
               data set, prior to processing and application of correction
               terms. While additional information may be added to the CIF
               as data are processed and transported between laboratories
               (possibly with the addition of a new _pd_block_id entry), the
               information in this section of the CIF will rarely be changed
               once data collection is complete.

               Where possible, measurements in this section should have no
               post-collection processing applied (normalizations, corrections,
               smoothing, zero-offset corrections etc.). Such corrected
               measurements should be recorded in the _pd_proc_ section.

               Data sets that are measured as counts, where a standard
               uncertainty can be considered equivalent to the standard
               deviation and where the standard deviation can be estimated
               as the square root of the number of counts recorded, should
               use the _pd_meas_counts_ fields. All other intensity values
               should be recorded using _pd_meas_intensity_.
;

_PD_PEAK_[PD]

CIF

This section contains peak information extracted from the

measured or, if present, the processed diffractogram. Each
peak in this table will have a unique label (see _pd_peak_id).
The reflections and phases associated with each peak will be
specified in other sections (see the _pd_refln_ and
_pd_phase_ sections).

Note that peak positions are customarily determined from the
processed diffractogram and thus corrections for position
and intensity will have been previously applied.

data_pd_peak_[pd]
    _name                       '_pd_peak_[pd]'
    _category                     category_overview
    _type                         null
    _definition
;              This section contains peak information extracted from the
               measured or, if present, the processed diffractogram. Each
               peak in this table will have a unique label (see _pd_peak_id).
               The reflections and phases associated with each peak will be
               specified in other sections (see the _pd_refln_ and
               _pd_phase_ sections).

               Note that peak positions are customarily determined from the
               processed diffractogram and thus corrections for position
               and intensity will have been previously applied.
;

_pd_peak_2theta

CIF

Data names:
_pd_peak_2theta_centroid
_pd_peak_2theta_maximum

Position of the centroid and maximum of a peak as a

2 angle in degrees.

data_pd_peak_2theta_
    loop_ _name                  '_pd_peak_2theta_centroid'
                                 '_pd_peak_2theta_maximum'
    _category                    pd_peak
    _type                        numb
    _type_conditions             esd
    _list                        yes
    _list_reference            '_pd_peak_id'
    _units                       deg
    _units_detail               'degrees'
    _enumeration_range           0.0:180.0
    _definition
;              Position of the centroid and maximum of a peak as a
               2\q angle in degrees.
;

_pd_peak_d_spacing

CIF

Peak position as a d-spacing in angstroms.

data_pd_peak_d_spacing
    _name                      '_pd_peak_d_spacing'
    _category                    pd_peak
    _type                        numb
    _type_conditions             esd
    _list                        yes
    _list_reference            '_pd_peak_id'
    _enumeration_range           0.0:
    _units                       A
    _units_detail               'angstroms'
    _definition
;              Peak position as a d-spacing in angstroms.
;

_pd_peak_id

CIF

An arbitrary code is assigned to each peak. Used to link with

_pd_refln_peak_id so that multiple hkl and/or phase
identifications can be assigned to a single peak.
Each peak will have a unique code. In cases
where two peaks are severely overlapped, it may be
desirable to list them as a single peak.

A peak ID must be included for every peak.

data_pd_peak_id
    _name                      '_pd_peak_id'
    _category                    pd_peak
    _type                        char
    _list                        yes
    _list_mandatory              yes
    _list_uniqueness           '_pd_peak_id'
    _list_link_child           '_pd_refln_peak_id'
    _definition
;              An arbitrary code is assigned to each peak. Used to link with
               _pd_refln_peak_id so that multiple hkl and/or phase
               identifications can be assigned to a single peak.
               Each peak will have a unique code. In cases
               where two peaks are severely overlapped, it may be
               desirable to list them as a single peak.

               A peak ID must be included for every peak.
;

_pd_peak_intensity

CIF

Integrated area for the peak, with the same scaling as

the _pd_proc_intensity_ values. It is good practice to
include s.u.'s for these values.

data_pd_peak_intensity
    _name                      '_pd_peak_intensity'
    _category                    pd_peak
    _type                        numb
    _type_conditions             esd
    _list                        yes
    _list_reference            '_pd_peak_id'
    _enumeration_range           0.0:
    _definition
;              Integrated area for the peak, with the same scaling as
               the _pd_proc_intensity_ values. It is good practice to
               include s.u.'s for these values.
;

_pd_peak_pk_height

CIF

The maximum intensity of the peak, either extrapolated

or the highest observed intensity value. The same
scaling is used for the _pd_proc_intensity_ values.
It is good practice to include s.u.'s for these values.

data_pd_peak_pk_height
    _name                      '_pd_peak_pk_height'
    _category                    pd_peak
    _type                        numb
    _type_conditions             esd
    _list                        yes
    _list_reference            '_pd_peak_id'
    _enumeration_range           0.0:
    _definition
;              The maximum intensity of the peak, either extrapolated
               or the highest observed intensity value. The same
               scaling is used for the _pd_proc_intensity_ values.
               It is good practice to include s.u.'s for these values.
;

_pd_peak_wavelength_id

CIF

Code identifying the wavelength appropriate for this peak

from the wavelengths in the _diffrn_radiation_ list.
(See _diffrn_radiation_wavelength_id.) Most commonly used
to distinguish K~1~ peaks from K~2~ or to designate
where K~1~ and K~2~ peaks cannot be resolved. For
complex peak tables with multiple superimposed peaks,
specify wavelengths in the reflection table using
_pd_refln_wavelength_id rather than identifying peaks by
wavelength.

data_pd_peak_wavelength_id
    _name                      '_pd_peak_wavelength_id'
    _category                    pd_peak
    _type                        char
    _list                        yes
    _list_reference            '_pd_peak_id'
    _list_link_parent          '_diffrn_radiation_wavelength_id'
    _definition
;              Code identifying the wavelength appropriate for this peak
               from the wavelengths in the _diffrn_radiation_ list.
               (See _diffrn_radiation_wavelength_id.) Most commonly used
               to distinguish K\a~1~ peaks from K\a~2~ or to designate
               where K\a~1~ and K\a~2~ peaks cannot be resolved. For
               complex peak tables with multiple superimposed peaks,
               specify wavelengths in the reflection table using
               _pd_refln_wavelength_id rather than identifying peaks by
               wavelength.
;

_pd_peak_width_2theta

CIF

Peak width as full-width at half-maximum expressed as

a 2 value in degrees.

data_pd_peak_width_2theta
    _name                      '_pd_peak_width_2theta'
    _category                    pd_peak
    _type                        numb
    _type_conditions             esd
    _list                        yes
    _list_reference            '_pd_peak_id'
    _enumeration_range           0.0:180.0
    _units                       deg
    _units_detail                degrees
    _definition
;              Peak width as full-width at half-maximum expressed as
               a 2\q value in degrees.
;

_pd_peak_width_d_spacing

CIF

Peak width as full-width at half-maximum expressed as

a d-spacing in angstroms.

data_pd_peak_width_d_spacing
    _name                      '_pd_peak_width_d_spacing'
    _category                    pd_peak
    _type                        numb
    _type_conditions             esd
    _list                        yes
    _list_reference            '_pd_peak_id'
    _enumeration_range           0.0:
    _units                       A
    _units_detail               'angstroms'
    _definition
;              Peak width as full-width at half-maximum expressed as
               a d-spacing in angstroms.
;

#............................ Crystalline Phase Assignments

_PD_PHASE_[PD]

CIF

This section contains a description of the crystalline phases

contributing to the powder diffraction data set. Note that if
multiple-phase Rietveld or other structural analysis is
performed, the structural results will be placed in different
data blocks, using CIF entries from the core CIF dictionary.

The _pd_phase_block_id entry points to the CIF block with
structural parameters for each crystalline phase. The
_pd_phase_id serves to link to _pd_refln_phase_id, which is
used to label peaks by phase.

data_pd_phase_[pd]
    _name                       '_pd_phase_[pd]'
    _category                     category_overview
    _type                         null

    _definition
;              This section contains a description of the crystalline phases
               contributing to the powder diffraction data set. Note that if
               multiple-phase Rietveld or other structural analysis is
               performed, the structural results will be placed in different
               data blocks, using CIF entries from the core CIF dictionary.

               The _pd_phase_block_id entry points to the CIF block with
               structural parameters for each crystalline phase. The
               _pd_phase_id serves to link to _pd_refln_phase_id, which is
               used to label peaks by phase.
;

_pd_phase_block_id

CIF

A block ID code identifying the phase contributing to

the diffraction peak. The data block containing the
crystallographic information for this phase will be
identified with a _pd_block_id code matching the
code in _pd_phase_block_id.

data_pd_phase_block_id
    _name                      '_pd_phase_block_id'
    _category                    pd_phase
    _type                        char
    _list                        yes
    _list_reference            '_pd_phase_id'
    _definition
;              A block ID code identifying the phase contributing to
               the diffraction peak. The data block containing the
               crystallographic information for this phase will be
               identified with a _pd_block_id code matching the
               code in _pd_phase_block_id.
;

_pd_phase_id

CIF

A code for each crystal phase used to link with

_pd_refln_phase_id.

data_pd_phase_id
    _name                      '_pd_phase_id'
    _category                    pd_phase
    _type                        char
    _list                        yes
    _list_mandatory              yes
    _list_link_child           '_pd_refln_phase_id'
    _list_uniqueness           '_pd_phase_id'
    _definition
;              A code for each crystal phase used to link with
               _pd_refln_phase_id.
;

_pd_phase_mass_%

CIF

Per cent composition of the specified crystal phase

expressed as the total mass of the component
with respect to the total mass of the specimen.

data_pd_phase_mass_%
    _name                      '_pd_phase_mass_%'
    _category                    pd_phase
    _type                        numb
    _type_conditions             esd
    _list                        yes
    _list_reference            '_pd_phase_id'
    _enumeration_range           0.0:100.0
    _definition
;              Per cent composition of the specified crystal phase
               expressed as the total mass of the component
               with respect to the total mass of the specimen.
;

_pd_phase_name

CIF

The name of the crystal phase identified by _pd_phase_id.

It may be designated as unknown or by a structure type etc.

data_pd_phase_name
    _name                      '_pd_phase_name'
    _category                    pd_phase
    _type                        char
    _list                        both
    _list_reference            '_pd_phase_id'
    _definition
;              The name of the crystal phase identified by _pd_phase_id.
               It may be designated as unknown or by a structure type etc.
;

#............................ Peak Reflection Identification

_PD_PREP_[PD]

CIF

This section contains descriptive information about how the

sample was prepared.

data_pd_prep_[pd]
    _name                       '_pd_prep_[pd]'
    _category                     category_overview
    _type                         null
    _definition
;              This section contains descriptive information about how the
               sample was prepared.
;

_pd_prep_conditions

CIF

A description of how the material was prepared

(reaction conditions etc.)

data_pd_prep_conditions
    _name                      '_pd_prep_conditions'
    _category                    pd_prep
    _type                        char
    _definition
;              A description of how the material was prepared
               (reaction conditions etc.)
;

_pd_prep_cool_rate

CIF

Cooling rate in kelvins per minute for samples prepared

at high temperatures. If the cooling rate is not linear
or is unknown (e.g. quenched samples), it should be
described in _pd_prep_conditions instead.

data_pd_prep_cool_rate
    _name                      '_pd_prep_cool_rate'
    _category                    pd_prep
    _type                        numb
    _type_conditions             esd
    _enumeration_range           0.0:
    _units                       Kmin^-1^
    _units_detail               'kelvins/minute'
    _definition
;              Cooling rate in kelvins per minute for samples prepared
               at high temperatures. If the cooling rate is not linear
               or is unknown (e.g. quenched samples), it should be
               described in _pd_prep_conditions instead.
;

_pd_prep_pressure

CIF

Preparation pressure of the sample in kilopascals. This

is particularly important for materials which are metastable
at the measurement pressure, _diffrn_ambient_pressure.

data_pd_prep_pressure
    _name                      '_pd_prep_pressure'
    _category                    pd_prep
    _type                        numb
    _type_conditions             esd
    _enumeration_range           0.0:
    _units                       kPa
    _units_detail               'kilopascals'
    _definition
;              Preparation pressure of the sample in kilopascals. This
               is particularly important for materials which are metastable
               at the measurement pressure, _diffrn_ambient_pressure.
;

_pd_prep_temperature

CIF

Preparation temperature of the sample in kelvins. This is

particularly important for materials which are metastable
at the measurement temperature, _diffrn_ambient_temperature.

data_pd_prep_temperature
    _name                      '_pd_prep_temperature'
    _category                    pd_prep
    _type                        numb
    _type_conditions             esd
    _enumeration_range           0.0:
    _units                       K
    _units_detail               'kelvin'
    _definition
;              Preparation temperature of the sample in kelvins. This is
               particularly important for materials which are metastable
               at the measurement temperature, _diffrn_ambient_temperature.
;

#............................. Characterisation Information

_PD_PROC_[PD]

CIF

This section contains the diffraction data set after processing

and application of correction terms. If the data set is
reprocessed, this section may be replaced (with the addition of
a new _pd_block_id entry).

data_pd_proc_[pd]
    _name                       '_pd_proc_[pd]'
    _category                     category_overview
    _type                         null
    _definition
;              This section contains the diffraction data set after processing
               and application of correction terms. If the data set is
               reprocessed, this section may be replaced (with the addition of
               a new _pd_block_id entry).
;

_pd_block_diffractogram_id

CIF

A block ID code (see _pd_block_id) that identifies

diffraction data contained in a data block other
than the current block. This will occur most frequently
when more than one set of diffraction data
is used for a structure determination. The data
block containing the diffraction data will contain
a _pd_block_id code matching the code in
_pd_block_diffractogram_id.

data_pd_block_diffractogram_id
    _name                      '_pd_block_diffractogram_id'
    _category                    pd_proc
    _type                        char
    _list                        yes
    _definition
;              A block ID code (see _pd_block_id) that identifies
               diffraction data contained in a data block other
               than the current block. This will occur most frequently
               when more than one set of diffraction data
               is used for a structure determination. The data
               block containing the diffraction data will contain
               a _pd_block_id code matching the code in
               _pd_block_diffractogram_id.
;

_PD_PROC_LS_[PD]

CIF

This section is used to define parameters relevant to a

least-squares fit to a powder diffractogram, using a Rietveld
or other full-profile (e.g. Pawley or Le Bail methods) fit.

Note that values in this section refer to full-pattern fitting.
Use the appropriate items for single-crystal analyses from the
core CIF dictionary for structure refinements using diffraction
intensities estimated from a powder diffractogram by
pattern-decomposition methods. Also note that many entries in
the core _refine_ls_ entries may also be useful (for example
_refine_ls_shift/su_*).

data_pd_proc_ls_[pd]
    _name                       '_pd_proc_ls_[pd]'
    _category                     category_overview
    _type                         null

    _definition
;              This section is used to define parameters relevant to a
               least-squares fit to a powder diffractogram, using a Rietveld
               or other full-profile (e.g. Pawley or Le Bail methods) fit.

               Note that values in this section refer to full-pattern fitting.
               Use the appropriate items for single-crystal analyses from the
               core CIF dictionary for structure refinements using diffraction
               intensities estimated from a powder diffractogram by 
               pattern-decomposition methods. Also note that many entries in 
               the core _refine_ls_ entries may also be useful (for example
               _refine_ls_shift/su_*).
;

_pd_proc_ls_background_function

CIF

Description of the background treatment mechanism used to

fit the data set.

For refinements where the background is computed as a
function that is fitted to minimize the difference between
the observed and calculated patterns, it is
recommended that in addition to a description of the
function (e.g. Chebychev polynomial), the actual equation(s)
used are included in TeX, or a programming language such
as Fortran or C. Include also the values used for the
coefficients used in the background function with their
s.u.'s. The background values for each data point
computed from the function should be specified in
_pd_proc_intensity_bkg_calc.

If background correction is performed using extrapolation
from a set of points at fixed locations, these points
should be defined using _pd_proc_intensity_bkg_fix, and
_pd_proc_ls_background_function should indicate the
extrapolation method (linear extrapolation, spline etc.).
_pd_proc_ls_background_function should also indicate how the
points were determined (automatically, by visual estimation
etc.) and whether the values were refined to improve the
agreement. The extrapolated background intensity value for
each data point should be specified in
_pd_proc_intensity_bkg_calc.

data_pd_proc_ls_background_function
    _name                      '_pd_proc_ls_background_function'
    _category                    pd_proc_ls
    _type                        char
    _definition
;              Description of the background treatment mechanism used to
               fit the data set.

               For refinements where the background is computed as a
               function that is fitted to minimize the difference between 
               the observed and calculated patterns, it is
               recommended that in addition to a description of the
               function (e.g. Chebychev polynomial), the actual equation(s)
               used are included in TeX, or a programming language such
               as Fortran or C. Include also the values used for the
               coefficients used in the background function with their
               s.u.'s. The background values for each data point
               computed from the function should be specified in
               _pd_proc_intensity_bkg_calc.

               If background correction is performed using extrapolation
               from a set of points at fixed locations, these points
               should be defined using _pd_proc_intensity_bkg_fix, and
               _pd_proc_ls_background_function should indicate the
               extrapolation method (linear extrapolation, spline etc.).
               _pd_proc_ls_background_function should also indicate how the
               points were determined (automatically, by visual estimation
               etc.) and whether the values were refined to improve the
               agreement. The extrapolated background intensity value for
               each data point should be specified in
               _pd_proc_intensity_bkg_calc.
;

_pd_proc_ls_peak_cutoff

CIF

Describes where peak-intensity computation is

discontinued as a fraction of the intensity of the
peak at maximum. Thus for a value of 0.005, the
tails of a diffraction peak are neglected
after the intensity has dropped below 0.5% of the
diffraction intensity at the maximum.

data_pd_proc_ls_peak_cutoff
    _name                      '_pd_proc_ls_peak_cutoff'
    _category                    pd_proc_ls
    _type                        numb
    _definition
;              Describes where peak-intensity computation is
               discontinued as a fraction of the intensity of the
               peak at maximum. Thus for a value of 0.005, the
               tails of a diffraction peak are neglected
               after the intensity has dropped below 0.5% of the
               diffraction intensity at the maximum.
;

_pd_proc_ls_pref_orient_corr

CIF

Description of the preferred-orientation correction if

such a correction is used. Omitting this entry
implies that no preferred-orientation correction
has been used. If a function form is used, it is
recommended that the actual equation in TeX, or a
programming language, is used to specify the function as
well as a giving a description. Include the value(s) used
for the correction with s.u.'s.

data_pd_proc_ls_pref_orient_corr
    _name                      '_pd_proc_ls_pref_orient_corr'
    _category                    pd_proc_ls
    _type                        char
    _definition
;              Description of the preferred-orientation correction if
               such a correction is used. Omitting this entry
               implies that no preferred-orientation correction
               has been used. If a function form is used, it is
               recommended that the actual equation in TeX, or a
               programming language, is used to specify the function as
               well as a giving a description. Include the value(s) used 
               for the correction with s.u.'s.
;

_pd_proc_ls_prof

CIF

Data names:
_pd_proc_ls_prof_R_factor
_pd_proc_ls_prof_wR_factor
_pd_proc_ls_prof_wR_expected

Rietveld/profile fit R factors.

Note that the R factor computed for Rietveld refinements
using the extracted reflection intensity values (often
called the Rietveld or Bragg R factor, R~B~) is not properly
a profile R factor. This R factor may be specified using
_refine_ls_R_I_factor. (Some authors report
_refine_ls_R_Fsqd_factor or _refine_ls_R_factor_all
as the Rietveld or Bragg R factor. While it is appropriate
to compute and report any or all of these R factors,
the names "Rietveld or Bragg R factor" refer strictly to
_refine_ls_R_I_factor.)

_pd_proc_ls_prof_R_factor, often called R~p~, is an
 unweighted fitness metric for the agreement between the
 observed and computed diffraction patterns.
    R~p~ = sum~i~ | I~obs~(i) - I~calc~(i) |
           / sum~i~ ( I~obs~(i) )
_pd_proc_ls_prof_wR_factor, often called R~wp~, is a
 weighted fitness metric for the agreement between the
 observed and computed diffraction patterns.
   R~wp~ = SQRT {
            sum~i~ ( w(i) [ I~obs~(i) - I~calc~(i) ]^2^ )
            / sum~i~ ( w(i) [I~obs~(i)]^2^ ) }

_pd_proc_ls_prof_wR_expected, sometimes called the
 theoretical R~wp~ or R~exp~, is a weighted fitness metric for
 the statistical precision of the data set. For an idealized fit,
 where all deviations between the observed intensities and
 those computed from the model are due to statistical
 fluctuations, the observed R~wp~ should match the expected
 R factor. In reality, R~wp~ will always be higher than
 R~exp~.
   R~exp~ = SQRT {
                  (n - p)  / sum~i~ ( w(i) [I~obs~(i)]^2^ ) }

 Note that in the above equations,
    w(i) is the weight for the ith data point (see
         _pd_proc_ls_weight).
    I~obs~(i) is the observed intensity for the ith data
         point, sometimes referred to as y~i~(obs) or
         y~oi~. (See _pd_meas_counts_total,
         _pd_meas_intensity_total or _pd_proc_intensity_total.)
    I~calc~(i) is the computed intensity for the ith data
         point with background and other corrections
         applied to match the scale of the observed data set,
         sometimes referred to as y~i~(calc) or
         y~ci~. (See _pd_calc_intensity_total.)
    n is the total number of data points (see
         _pd_proc_number_of_points) less the number of
         data points excluded from the refinement.
    p is the total number of refined parameters.

data_pd_proc_ls_prof_
    loop_ _name                 '_pd_proc_ls_prof_R_factor'
                                '_pd_proc_ls_prof_wR_factor'
                                '_pd_proc_ls_prof_wR_expected'
    _category                    pd_proc_ls
    _type                        numb
    _enumeration_range           0.0:
    _definition
;              Rietveld/profile fit R factors.

               Note that the R factor computed for Rietveld refinements
               using the extracted reflection intensity values (often
               called the Rietveld or Bragg R factor, R~B~) is not properly
               a profile R factor. This R factor may be specified using
               _refine_ls_R_I_factor. (Some authors report
               _refine_ls_R_Fsqd_factor or _refine_ls_R_factor_all
               as the Rietveld or Bragg R factor. While it is appropriate
               to compute and report any or all of these R factors,
               the names "Rietveld or Bragg R factor" refer strictly to
               _refine_ls_R_I_factor.)

              _pd_proc_ls_prof_R_factor, often called R~p~, is an
                unweighted fitness metric for the agreement between the
                observed and computed diffraction patterns.
                   R~p~ = sum~i~ | I~obs~(i) - I~calc~(i) |
                          / sum~i~ ( I~obs~(i) )
              _pd_proc_ls_prof_wR_factor, often called R~wp~, is a
                weighted fitness metric for the agreement between the
                observed and computed diffraction patterns.
                  R~wp~ = SQRT {
                           sum~i~ ( w(i) [ I~obs~(i) - I~calc~(i) ]^2^ )
                           / sum~i~ ( w(i) [I~obs~(i)]^2^ ) }

              _pd_proc_ls_prof_wR_expected, sometimes called the
                theoretical R~wp~ or R~exp~, is a weighted fitness metric for
                the statistical precision of the data set. For an idealized fit,
                where all deviations between the observed intensities and
                those computed from the model are due to statistical
                fluctuations, the observed R~wp~ should match the expected
                R factor. In reality, R~wp~ will always be higher than
                R~exp~.
                  R~exp~ = SQRT {
                                 (n - p)  / sum~i~ ( w(i) [I~obs~(i)]^2^ ) }

                Note that in the above equations,
                   w(i) is the weight for the ith data point (see
                        _pd_proc_ls_weight).
                   I~obs~(i) is the observed intensity for the ith data
                        point, sometimes referred to as y~i~(obs) or
                        y~oi~. (See _pd_meas_counts_total,
                        _pd_meas_intensity_total or _pd_proc_intensity_total.)
                   I~calc~(i) is the computed intensity for the ith data
                        point with background and other corrections
                        applied to match the scale of the observed data set,
                        sometimes referred to as y~i~(calc) or
                        y~ci~. (See _pd_calc_intensity_total.)
                   n is the total number of data points (see
                        _pd_proc_number_of_points) less the number of
                        data points excluded from the refinement.
                   p is the total number of refined parameters.
;

_pd_proc_ls_profile_function

CIF

Description of the profile function used to

fit the data set. If a function form is used, it is
recommended that the actual equation in TeX, or a
programming language, is used to specify the function as
well as giving a description. Include the values used
for the profile-function coefficients and their s.u.'s.

data_pd_proc_ls_profile_function
    _name                      '_pd_proc_ls_profile_function'
    _category                    pd_proc_ls
    _type                        char
    _definition
;              Description of the profile function used to
               fit the data set. If a function form is used, it is
               recommended that the actual equation in TeX, or a
               programming language, is used to specify the function as
               well as giving a description. Include the values used 
               for the profile-function coefficients and their s.u.'s.
;

_pd_proc_ls_special_details

CIF

Additional characterization information relevant to

non-routine steps used for refinement of a structural model
that cannot be specified elsewhere.

data_pd_proc_ls_special_details
    _name                      '_pd_proc_ls_special_details'
    _category                    pd_proc_ls
    _type                        char
    _definition
;              Additional characterization information relevant to
               non-routine steps used for refinement of a structural model
               that cannot be specified elsewhere.
;

_PD_REFLN_[PD]

CIF

This section provides a mechanism to identify each peak in the

peak-table section (_pd_peak_) with the phase(s) (_pd_phase_id)
and the reflection indices (_refln_index_) associated with the
peak.  There are no restrictions on the number of phases or
reflections associated with an observed peak. Reflections may
also be included that are not observed; use '.' for the
_pd_refln_peak_id.

data_pd_refln_[pd]
    _name                       '_pd_refln_[pd]'
    _category                     category_overview
    _type                         null
    _definition
;              This section provides a mechanism to identify each peak in the
               peak-table section (_pd_peak_) with the phase(s) (_pd_phase_id)
               and the reflection indices (_refln_index_) associated with the
               peak.  There are no restrictions on the number of phases or
               reflections associated with an observed peak. Reflections may
               also be included that are not observed; use '.' for the
               _pd_refln_peak_id.
;

_PD_SPEC_[PD]

CIF

This section contains information about the specimen used

for measurement of the diffraction data set. Note that
information about the sample (the batch of material from which
the specimen was obtained) is specified in _pd_prep_.

Example:

_pd_spec_mounting               ?
    _pd_spec_mount_mode             transmission
    _pd_spec_orientation            horizontal
    _pd_spec_preparation            ?

data_pd_spec_[pd]
    _name                       '_pd_spec_[pd]'
    _category                     category_overview
    _type                         null
    loop_
        _example
        _example_detail
#----------------------------------------------------------------------------
;
    _pd_spec_mounting               ?
    _pd_spec_mount_mode             transmission
    _pd_spec_orientation            horizontal
    _pd_spec_preparation            ?
;
;
    Example 1.
;
#----------------------------------------------------------------------------
    _definition
;              This section contains information about the specimen used
               for measurement of the diffraction data set. Note that 
               information about the sample (the batch of material from which 
               the specimen was obtained) is specified in _pd_prep_.
;

_pd_spec_description

CIF

A description of the specimen, such as the source of the

specimen, identification of standards, mixtures etc.

data_pd_spec_description
     _name                     '_pd_spec_description'
     _category                   pd_spec
     _type                       char
     _definition
;               A description of the specimen, such as the source of the
                specimen, identification of standards, mixtures etc.
;

_pd_spec_mount_mode

CIF

A code describing the beam path through the specimen.

data_pd_spec_mount_mode
    _name                      '_pd_spec_mount_mode'
    _category                    pd_spec
    _type                        char
    loop_ _enumeration           reflection
                                 transmission
    _definition
;              A code describing the beam path through the specimen.
;

_pd_spec_mounting

CIF

A description of how the specimen is mounted.

Examples:

vanadium can with He exchange gas

quartz capillary

packed powder pellet

drifted powder on off-cut Si

drifted powder on Kapton film

data_pd_spec_mounting
    _name                      '_pd_spec_mounting'
    _category                    pd_spec
    _type                        char
    loop_ _example               'vanadium can with He exchange gas'
                                 'quartz capillary'
                                 'packed powder pellet'
                                 'drifted powder on off-cut Si'
                                 'drifted powder on Kapton film'
    _definition
;              A description of how the specimen is mounted.
;

_pd_spec_orientation

CIF

The orientation of the  () and 2 axis.

Note that this axis is parallel to the specimen axial axis
and perpendicular to the plane containing the incident and
scattered beams.

Thus for a horizontal orientation, scattering
measurements are made in a plane perpendicular to the
ground (the 2 axis is parallel to the ground);
for vertical orientation, scattering measurements are
made in a plane parallel with the ground (the 2 axis
is perpendicular to the ground). `Both' is appropriate for
experiments where measurements are made in both planes,
for example using two-dimensional detectors.

data_pd_spec_orientation
    _name                      '_pd_spec_orientation'
    _category                    pd_spec
    _type                        char
    loop_ _enumeration           horizontal
                                 vertical
                                 both
    _definition
;              The orientation of the \w (\q) and 2\q axis.
               Note that this axis is parallel to the specimen axial axis
               and perpendicular to the plane containing the incident and
               scattered beams.

               Thus for a horizontal orientation, scattering
               measurements are made in a plane perpendicular to the
               ground (the 2\q axis is parallel to the ground);
               for vertical orientation, scattering measurements are
               made in a plane parallel with the ground (the 2\q axis
               is perpendicular to the ground). `Both' is appropriate for
               experiments where measurements are made in both planes,
               for example using two-dimensional detectors.
;

_pd_spec_preparation

CIF

A description of the preparation steps for producing the

diffraction specimen from the sample. Include any procedures
related to grinding, sieving, spray drying etc. For
information relevant to how the sample is synthesized, use
the _pd_prep_ entries.

Examples:

wet grinding in acetone

sieved through a 44 micron (325 mesh/inch) sieve

spray dried in water with 1% clay

data_pd_spec_preparation
    _name                      '_pd_spec_preparation'
    _category                    pd_spec
    _type                        char
    loop_ _example               'wet grinding in acetone'
                              'sieved through a 44 micron (325 mesh/inch) sieve'
                                 'spray dried in water with 1% clay'
    _definition
;              A description of the preparation steps for producing the
               diffraction specimen from the sample. Include any procedures
               related to grinding, sieving, spray drying etc. For
               information relevant to how the sample is synthesized, use
               the _pd_prep_ entries.
;

_pd_spec_shape

CIF

A code describing the specimen shape.

data_pd_spec_shape
    _name                      '_pd_spec_shape'
    _category                    pd_spec
    _type                        char
    loop_ _enumeration           cylinder
                                 flat_sheet
                                 irregular
    _definition
;              A code describing the specimen shape.
;

_pd_spec_size

CIF

Data names:
_pd_spec_size_axial
_pd_spec_size_equat
_pd_spec_size_thick

The size of the specimen in three mutually perpendicular

directions in millimetres.
The perpendicular to the plane containing the incident
and scattered beam is the *_axial direction.
In transmission geometry, the scattering vector is parallel
to *_equat and in reflection geometry the scattering vector is
parallel to *_thick.

data_pd_spec_size_
    loop_ _name                '_pd_spec_size_axial'
                               '_pd_spec_size_equat'
                               '_pd_spec_size_thick'
    _category                    pd_spec
    _type                        numb
    _units                       mm
    _units_detail               'millimetres'
    _enumeration_range           0.0:
    _definition
;              The size of the specimen in three mutually perpendicular
               directions in millimetres.
               The perpendicular to the plane containing the incident
               and scattered beam is the *_axial direction.
               In transmission geometry, the scattering vector is parallel
               to *_equat and in reflection geometry the scattering vector is
               parallel to *_thick.

;

_pd_spec_special_details

CIF

Descriptive information about the specimen that cannot be

included in other data items.

data_pd_spec_special_details
    _name                      '_pd_spec_special_details'
    _category                   pd_spec
    _type                       char
    _definition
;              Descriptive information about the specimen that cannot be
               included in other data items.
;

#............................ Instrument parameters

PD_CALIBRATION

CIF

_pd_calibration_conversion_eqn

CIF

The calibration function for converting a channel number

supplied in _pd_meas_detector_id for a position-sensitive
or energy-dispersive detector or the distance supplied in
_pd_meas_position to Q, energy, angle etc.
Use _pd_calib_std_external_ to define a pointer
to the file or data block containing the information used
to define this function.

Example:

2~actual~ = 2~setting~ + arctan(
             cos(P~1~) / {1/[P~0~ (CC - CH~0~ - P~2~ CC^2^)] - sin(P~1~)} )

data_pd_calibration_conversion_eqn
    _name                      '_pd_calibration_conversion_eqn'
    _category                    pd_calibration
    _type                        char
    _example
; 2\q~actual~ = 2\q~setting~ + arctan(
             cos(P~1~) / {1/[P~0~ (CC - CH~0~ - P~2~ CC^2^)] - sin(P~1~)} )
;
    _definition
;              The calibration function for converting a channel number
               supplied in _pd_meas_detector_id for a position-sensitive
               or energy-dispersive detector or the distance supplied in
               _pd_meas_position to Q, energy, angle etc.
               Use _pd_calib_std_external_ to define a pointer
               to the file or data block containing the information used
               to define this function.
;

_pd_calibration_special_details

CIF

Description of how the instrument was

calibrated, particularly for instruments where
calibration information is used to make hardware
settings that would otherwise be invisible once data
collection is completed. Do not use this item to specify
information that can be specified using other _pd_calib_
items.

data_pd_calibration_special_details
    _name                      '_pd_calibration_special_details'
    _category                    pd_calibration
    _type                        char
    _definition
;              Description of how the instrument was
               calibrated, particularly for instruments where
               calibration information is used to make hardware
               settings that would otherwise be invisible once data
               collection is completed. Do not use this item to specify
               information that can be specified using other _pd_calib_
               items.
;

#............................ Specimen parameters

PD_MEAS_INFO

CIF

_pd_meas_info_author_address

CIF

The address of the person who measured the data set. If there

is more than one person, this will be looped with
_pd_meas_info_author_name.

data_pd_meas_info_author_address
    _name                      '_pd_meas_info_author_address'
    _category                    pd_meas_info
    _type                        char
    _list                        both
    _list_reference            '_pd_meas_info_author_name'
    _definition
;              The address of the person who measured the data set. If there
               is more than one person, this will be looped with
               _pd_meas_info_author_name.
;

_pd_meas_info_author_email

CIF

The e-mail address of the person who measured the data set. If

there is more than one person, this will be looped with
_pd_meas_info_author_name.

data_pd_meas_info_author_email
    _name                      '_pd_meas_info_author_email'
    _category                    pd_meas_info
    _type                        char
    _list                        both
    _list_reference            '_pd_meas_info_author_name'
    _definition
;              The e-mail address of the person who measured the data set. If
               there is more than one person, this will be looped with
               _pd_meas_info_author_name.
;

_pd_meas_info_author_fax

CIF

The fax number of the person who measured the data set. If

there is more than one person, this will be looped with
_pd_meas_info_author_name. The recommended style is
the international dialing prefix, followed by the area code in
parentheses, followed by the local number with no spaces.

data_pd_meas_info_author_fax
    _name                      '_pd_meas_info_author_fax'
    _category                    pd_meas_info
    _type                        char
    _list                        both
    _list_reference            '_pd_meas_info_author_name'
    _definition
;              The fax number of the person who measured the data set. If
               there is more than one person, this will be looped with
               _pd_meas_info_author_name. The recommended style is
               the international dialing prefix, followed by the area code in
               parentheses, followed by the local number with no spaces.
;

_pd_meas_info_author_name

CIF

The name of the person who measured the data set. The family

name(s), followed by a comma and including any dynastic
components, precedes the first name(s) or initial(s).
For more than one person use a loop to specify multiple values.

data_pd_meas_info_author_name
    _name                      '_pd_meas_info_author_name'
    _category                    pd_meas_info
    _type                        char
    _list                        both
    _definition
;              The name of the person who measured the data set. The family
               name(s), followed by a comma and including any dynastic
               components, precedes the first name(s) or initial(s).
               For more than one person use a loop to specify multiple values.
;

_pd_meas_info_author_phone

CIF

The telephone number of the person who measured the data set.

If there is more than one person, this will be looped with
_pd_meas_info_author_name. The recommended style is
the international dialing prefix, followed by the area code in
parentheses, followed by the local number with no spaces.

data_pd_meas_info_author_phone
    _name                      '_pd_meas_info_author_phone'
    _category                    pd_meas_info
    _type                        char
    _list                        both
    _list_reference            '_pd_meas_info_author_name'
    _definition
;              The telephone number of the person who measured the data set.
               If there is more than one person, this will be looped with
               _pd_meas_info_author_name. The recommended style is
               the international dialing prefix, followed by the area code in
               parentheses, followed by the local number with no spaces.
;

PD_MEAS_METHOD

CIF

_pd_meas_2theta_fixed

CIF

The 2 diffraction angle in degrees for measurements

in a white-beam fixed-angle experiment. For measurements
where 2 is scanned, see _pd_meas_2theta_scan or
_pd_meas_2theta_range_.

data_pd_meas_2theta_fixed
    _name                      '_pd_meas_2theta_fixed'
    _category                    pd_meas_method
    _type                        numb
    _type_conditions             esd
    _enumeration_range           -180.0:360.0
    _definition
;              The 2\q diffraction angle in degrees for measurements
               in a white-beam fixed-angle experiment. For measurements
               where 2\q is scanned, see _pd_meas_2theta_scan or
               _pd_meas_2theta_range_.
;

_pd_meas_2theta_range

CIF

Data names:
_pd_meas_2theta_range_min
_pd_meas_2theta_range_max
_pd_meas_2theta_range_inc

The range of 2 diffraction angles in degrees for the

measurement of intensities. These may be used in place of the
_pd_meas_2theta_scan values for data sets measured with a
constant step size.

data_pd_meas_2theta_range_
    loop_ _name                '_pd_meas_2theta_range_min'
                               '_pd_meas_2theta_range_max'
                               '_pd_meas_2theta_range_inc'
    _category                    pd_meas_method
    _type                        numb
    _enumeration_range           -180.0:360.0
    _definition
;              The range of 2\q diffraction angles in degrees for the
               measurement of intensities. These may be used in place of the
               _pd_meas_2theta_scan values for data sets measured with a
               constant step size.
;

_pd_meas_datetime_initiated

CIF

The date and time of the data-set measurement. Entries follow

the standard CIF format 'yyyy-mm-ddThh:mm:ss+zz'. Use
of seconds and a time zone is optional, but use of hours
and minutes is strongly encouraged. Where possible, give the
time when the measurement was started rather than when
it was completed.

Example:

1990-07-13T14:40

data_pd_meas_datetime_initiated
    _name                      '_pd_meas_datetime_initiated'
    _category                    pd_meas_method
    _type                        char
    _example                     1990-07-13T14:40
    _definition
;              The date and time of the data-set measurement. Entries follow
               the standard CIF format 'yyyy-mm-ddThh:mm:ss+zz'. Use
               of seconds and a time zone is optional, but use of hours
               and minutes is strongly encouraged. Where possible, give the
               time when the measurement was started rather than when
               it was completed.
;

_pd_meas_number_of_points

CIF

The total number of points in the measured

diffractogram.

data_pd_meas_number_of_points
    _name                      '_pd_meas_number_of_points'
    _category                    pd_meas_method
    _type                        numb
    _enumeration_range           1:
    _definition
;              The total number of points in the measured
               diffractogram.
;

_pd_meas_rocking_axis

CIF

Description of the axis (or axes) used to rotate or rock the

specimen for better randomization of crystallites
(see _pd_meas_rocking_angle).

data_pd_meas_rocking_axis
    _name                      '_pd_meas_rocking_axis'
    _category                    pd_meas_method
    _type                        char
    loop_ _enumeration           chi
                                 omega
                                 phi
    _definition
;              Description of the axis (or axes) used to rotate or rock the
               specimen for better randomization of crystallites
               (see _pd_meas_rocking_angle).
;

_pd_meas_scan_method

CIF

Code identifying the method for scanning reciprocal space.

The designation `fixed' should be used for measurements where
film, a stationary position-sensitive or area detector
or other non-moving detection mechanism is used to
measure diffraction intensities.

data_pd_meas_scan_method
    _name                      '_pd_meas_scan_method'
    _category                    pd_meas_method
    _type                        char
    loop_ _enumeration
          _enumeration_detail    step    'step scan'
                                 cont    'continuous scan'
                                 tof     'time of flight'
                                 disp    'energy dispersive'
                                 fixed   'stationary detector'
    _definition
;              Code identifying the method for scanning reciprocal space.
               The designation `fixed' should be used for measurements where
               film, a stationary position-sensitive or area detector
               or other non-moving detection mechanism is used to
               measure diffraction intensities.
;

_pd_meas_special_details

CIF

Special details of the diffraction measurement process.

Include information about source instability, degradation etc.
However, this item should not be used to record information
that can be specified in other _pd_meas_ entries.

data_pd_meas_special_details
    _name                      '_pd_meas_special_details'
    _category                    pd_meas_method
    _type                        char
    _definition
;              Special details of the diffraction measurement process.
               Include information about source instability, degradation etc.
               However, this item should not be used to record information
               that can be specified in other _pd_meas_ entries.
;

_pd_meas_units_of_intensity

CIF

Units for intensity measurements when _pd_meas_intensity_

is used. Note that use of 'counts' or 'counts per second'
here is strongly discouraged: convert the intensity
measurements to counts and use _pd_meas_counts_ and
_pd_meas_step_count_time instead of _pd_meas_intensity_.

Examples:

estimated from strip chart

arbitrary, from film density

counts, with automatic dead-time correction applied

data_pd_meas_units_of_intensity
    _name                      '_pd_meas_units_of_intensity'
    _category                    pd_meas_method
    _type                        char
    loop_ _example        'estimated from strip chart'
                          'arbitrary, from film density'
                          'counts, with automatic dead-time correction applied'
    _definition
;              Units for intensity measurements when _pd_meas_intensity_
               is used. Note that use of 'counts' or 'counts per second'
               here is strongly discouraged: convert the intensity
               measurements to counts and use _pd_meas_counts_ and
               _pd_meas_step_count_time instead of _pd_meas_intensity_.
;

#........................... Calibration Information

PD_PEAK_METHOD

CIF

_pd_peak_special_details

CIF

Detailed description of any non-routine processing steps

used for peak determination or other comments
related to the peak table that cannot be given elsewhere.

data_pd_peak_special_details
    _name                      '_pd_peak_special_details'
    _category                    pd_peak_method
    _type                        char
    _definition
;              Detailed description of any non-routine processing steps
               used for peak determination or other comments
               related to the peak table that cannot be given elsewhere.
;

REFLN

CIF

_pd_refln_peak_id

CIF

Code which identifies the powder diffraction peak that

contains the current reflection. This code must match a
_pd_peak_id code.

data_pd_refln_peak_id
    _name                      '_pd_refln_peak_id'
    _category                    refln
    _type                        char
    _list                        yes
    loop_ _list_reference      '_refln_index_h'
                               '_refln_index_k'
                               '_refln_index_l'
    _list_link_parent          '_pd_peak_id'
    _definition
;              Code which identifies the powder diffraction peak that
               contains the current reflection. This code must match a
               _pd_peak_id code.
;

_pd_refln_phase_id

CIF

Code which identifies the crystal phase associated with this

reflection. This code must match a _pd_phase_id code.

data_pd_refln_phase_id
    _name                      '_pd_refln_phase_id'
    _category                    refln
    _type                        char
    _list                        yes
    loop_ _list_reference      '_refln_index_h'
                               '_refln_index_k'
                               '_refln_index_l'
    _list_link_parent          '_pd_phase_id'
    _definition
;              Code which identifies the crystal phase associated with this
               reflection. This code must match a _pd_phase_id code.
;

_pd_refln_wavelength_id

CIF

Code which identifies the wavelength associated with the

reflection and the peak pointed to by _pd_refln_peak_id.
This code must match a _diffrn_radiation_wavelength_id code.

data_pd_refln_wavelength_id
    _name                      '_pd_refln_wavelength_id'
    _category                    refln
    _type                        char
    _list                        yes
    loop_ _list_reference      '_refln_index_h'
                               '_refln_index_k'
                               '_refln_index_l'
    _list_link_parent          '_diffrn_radiation_wavelength_id'
    _definition
;              Code which identifies the wavelength associated with the
               reflection and the peak pointed to by _pd_refln_peak_id.
               This code must match a _diffrn_radiation_wavelength_id code.
;

#............................. Sample Preparation Information

Revision history

1991-08-28  Initial definitions                                  B.H. Toby

1991-09-15  More definitions added                               B.H. Toby

1991-09-21  Still More definitions                               B.H. Toby

1991-09-24  Some updates from down under  |:-)                   S.R. Hall

1991-10-07  Unable to leave well enough alone...                 B.H. Toby

1991-10-10  Some additional fine tuning   (-:|                   S.R. Hall

1991-10-14  Minor touchups                                       B.H. Toby

1991-12-08  Back to Work...                                      B.H. Toby

1992-01-07  Add _pd_refln_ to allow for mixtures                 B.H. Toby

1992-02-07  Some redefinitions                                   S.R. Hall

1992-02-25  Defining standards is a fiddly business              S.R. Hall

1992-03-18  And still more...                                    B.H. Toby

1992-05-22  Minor cleanup                                        B.H. Toby

1992-05-23  Quasar says that all is OK now...                    S.R. Hall

1992-05-30  Changes from comments @ APD-II                       B.H. Toby

1992-08-18  Add calculated pattern definitions                   B.H. Toby

1992-08-28  Change 'powder' to 'pw'                              B.H. Toby

1992-08-31  Major overhaul of some definitions                   B.H. Toby

1992-09-01  Small adjustments                                    S.R. Hall

1992-10-01  Change 'pw' to 'pd'                                  B.H. Toby

1993-04-16  Change usage for multiple detectors                  B.H. Toby

1993-04-19  Change *_raw_ to *_meas_; *_sample_ to *_samp_
Install new DDL commands; new *_phase_ group         S.R. Hall

1993-05-22  Fix _pd_calib_ defs; Minor editing                   B.H. Toby

1993-05-31  Still more minor editing                             B.H. Toby

1993-06-02  Application of new DDL commands                      S.R. Hall

1993-08-13  Last stop before Beijing, more descriptive entries &
more descriptive text added; support for film data.  B.H. Toby

1993-10-27  My two cents worth                                   I.D. Brown

1994-01-23  Change two to 2.5; sample to specimen.               B.H. Toby

1994-03-13  Change date/time usage
Be more careful about pd_proc usage: separate data
& processing conditions                              B.H. Toby

1994-04-11  Start work on categories: move all diffractogram
items (that might ever be in a single loop) into
pd_data.                                             B.H. Toby

1994-05-11  Start revisions based on I.D. Brown's comments       B.H. Toby

1994-06-25  Complete revisions prior to ACA                      B.H. Toby

1994-10-27  Working draft                                        B.H. Toby

1995-10-23  Implemented _units and _units_detail                 B. McMahon

1995-10-24  Transferred _pd_instr_radiation_probe to the core
as _diffrn_radiation_probe                           B. McMahon

1997-01-30  Final cleanup: removed _nm units; add units to
definitions; add _pd_block_diffractogram_id;
change _pd_meas_distance_value to _pd_meas_position;
remove _pd_proc_wavelength_nm, _pd_proc_d_spacing_nm;
_pd_proc_recip_len_Q_nm, and _pd_peak_d_spacing_nm
B.H. Toby

1997-01-31  Changed dictionary_definition to category_overview;
removed data_include_dependent_dictionaries and global_
blocks; some typos fixed                             B. McMahon

1997-02-12  Some typos fixed                                     B. McMahon

1997-02-18  References to e.s.d. changed to s.u. etc.
Notation for Bragg and expected R factors changed to
R~B~ and R~exp~
B. McMahon

1997-03-10  Category of _pd_refln_ things changed to 'refln'; category of`
_pd_proc_number_of_points changed to 'pd_proc_info'; some
rewording of descriptions involving s.u.s according to BT;
changed 'samp' to 'spec' in many datanames relating distances
to specimen; changed style of these and similar to *_src/spec
etc; _pd_calc_method no longer has '_list yes'; _list_uniqueness
deleted from _pd_refln_peak_id; use of '.' instead of '?'
recommended in a couple of places; addition of example to
_pd_calib_conversion_eqn; '_pd_proc_intensity_calc_bkg' and
'_fix_bkg' changed to '_pd_proc_intensity_bkg_calc' and '_fix'
B. McMahon

1997-03-12  Category of _pd_calib_ things changed to 'pd_calib';
_pd_calib_conversion_eqn and *_special_details renamed as
_pd_calibration_* and assigned to category 'pd_calibration'
Alphabetised entries within category.
B. McMahon

1997-03-17  Copyediting changes to punctuation and spelling.     B. McMahon

1997-10-29  Changed _pd_calib_std_external_id to
_pd_calib_std_external_block_id. Moved _pd_proc_2theta_range_ to
category pd_proc_info (because not looped with other pd_data
items).
B. McMahon

1997-10-29  Release version 1.0                                  B. McMahon

2005-01-07  NJA: minor corrections to hyphenation, spelling and punctuation
pd_data_[pd]: Example 3, second loop _pd_calc_2theta_scan
changed to _pd_proc_2theta_corrected
_pd_instr_cons_illum_len: definition rephrased
_pd_phase_[pd]: first sentence of definition rephrased
_pd_proc_ls_background_function: second paragraph of
definition rephrased

		contents
		indexes
		sample pages
		purchase
		CIF dictionaries

Crystallographic Information Framework

CIF dictionary browser

cif_pd.dic CIF dictionary

Category view of data-item definitions

Revision history

International Tables for Crystallography

Volume G: Definition and exchange of crystallographic data

Edited by S. R. Hall and B. McMahon

IUCrData