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Re: Approval of CIF core changes for 2.3



Dear David

I am sending as an attachment a revised copy of the document that was posted
on your behalf a few days ago. It incorporates Howard's typos and minor
rewordings. I haven't deleted the Z_prime entry, though you have indicated
that you will pull it from consideration at this stage (though I remark that
there have been requests from other sources for a record of Z', so finding a
sound definition would be a useful priority for the next version). Nor have
I included either of Howard's alternative definitions for
_space_group_symop_operation_xyz

I have also corrected a few syntax errors and incorrect DDL names, and
made a few light editorial changes. The technical details are almost
certainly of no interest to anyone, but can be inspected if necessary in the
colour-coded file http://agate.iucr.org/cif/cif_core/minoredits.html

If you prefer some different indication of the changes (e.g. a "diff"
listing), please let me know.

Best wishes
Brian
##################################################
# 
#    REVISIONS TO CIF_CORE_2.3.DIC
#    ITEMS SUBJECT TO APPROVAL BY CORE DMG AND COMCIFS
#
##################################################
#
# Accumulated list of tentatively approved items.
#
# The following new datanames are proposed in this draft of the revisions to
# the core CIF dictionary.
#
#     ATOM SITE
#        _atom_site_fract_ (modify)
#        _atom_site_refinement_flags (replace with the following)
#        _atom_site_refinement_flags_posn
#        _atom_site_refinement_flags_adp
#        _atom_site_refinement_flags_occupancy
#    ATOM SITES
#       _atom_sites_special_details
#     CELL
#        _cell_formula_units_Z_prime
#        _cell_reciprocal_angle_alpha
#        _cell_reciprocal_angle_beta
#        _cell_reciprocal_angle_gamma
#        _cell_reciprocal_length_a
#        _cell_reciprocal_length_b
#        _cell_reciprocal_length_c
#     CHEMICAL
#        _chemical_melting_point (modify)
#        _chemical_melting_point_gt
#        _chemical_melting_point_lt
#        _chemical_properties_biological
#        _chemical_properties_physical
#        _chemical_temperature_decomposition
#        _chemical_temperature_decomposition_gt
#        _chemical_temperature_decomposition_lt
#        _chemical_temperature_sublimation
#        _chemical_temperature_sublimation_gt
#        _chemical_temperature_sublimation_lt
#     CITATION
#        _citation_database_id_CSD
#     DATABASE
#        _database_code_depnum_ccdc_fiz
#        _database_code_depnum_ccdc_journal
#        _database_code_depnum_ccdc_archive
#        _database_CSD_history
#     DIFFRN
#        _diffrn_ambient_pressure_gt
#        _diffrn_ambient_pressure_lt
#        _diffrn_ambient_temperature_gt
#        _diffrn_ambient_temperature_lt
#     DIFFRN_SOURCE
#        _diffrn_source_take-off_angle
#     DIFFRN_STANDARDS
#        _diffrn_standards_decay_%_lt
#     DIFFRN_REFLNS
#        _diffrn_reflns_measured_fraction_resolution_full
#        _diffrn_reflns_measured_fraction_resolution_max
#        _diffrn_reflns_resolution_full
#        _diffrn_reflns_resolution_max
#     EXPTL_CRYSTAL
#        _exptl_crystal_colour_primary
#        _exptl_crystal_colour_modifier
#        _exptl_crystal_colour_lustre
#        _exptl_crystal_density_meas_gt
#        _exptl_crystal_density_meas_lt
#        _exptl_crystal_density_meas_temp_gt
#        _exptl_crystal_density_meas_temp_lt
#        _exptl_crystal_recrystallization_method
#     PUBL
#        _publ_contact_author_id_iucr
#     PULB_AUTHOR
#        _publ_author_id_iucr
#     REFINE
#        _refine_ls_shift/su_max_lt
#        _refine_ls_shift/su_mean_lt
#     SPACE_GROUP     (General information on the space group)
#        _space_group_crystal_system
#        _space_group_id            (Parent to various .sg_id's)
#        _space_group_IT_number
#        _space_group_name_Hall
#        _space_group_name_H-M_alt
#     SPACE_GROUP_SYMOP               (Symmetry operations)
#        _space_group_symop_id       (parent to various .symop_id's)
#        _space_group_symop_operation_xyz
#        _space_group_symop_sg_id
#
##################################################

##################################################
#
#   ATOM SITE
#
##################################################

data_atom_site_fract_
    loop_ _name                '_atom_site_fract_x'
                               '_atom_site_fract_y'
                               '_atom_site_fract_z'
    _category                    atom_site
    _type                        numb
    _type_conditions             esd
    _related_item              '_atom_site_Cartn_'
    _related_function            alternate
    _list                        yes
    _list_reference            '_atom_site_label'
#    _enumeration_default         0.0
    _definition
;              Atom site coordinates as fractions of the _cell_length_ values.
;
# COMMENT: The default should be deleted since it makes no sense.  If the
# coordinates are defaulted it is, presumably, because they are not known, not
# because the atom is at the origin.
# STATUS: Preliminary approval 02-09-23

# COMMENT: The proposal is to replace the following item by the subsequent 
# three items.  The
# problem with the current definition is that it requires the character field
# to be parsed since any of the seven flags may appear in any order.  The
# replacement items define unique flags for each possibility.

data_atom_site_refinement_flags
    _name                      '_atom_site_refinement_flags'
    _category                    atom_site
    _type                        char
    _list                        yes
    _list_reference            '_atom_site_label'
  loop_
   _related_item
   _related_function
    '_atom_site_refinement_flags_posn'        replace
    '_atom_site_refinement_flags_adp'         replace
    '_atom_site_refinement_flags_occupancy'   replace
   loop_ _enumeration
         _enumeration_detail   . 'no refinement constraints'
                               S 'special position constraint on site'
                               G 'rigid group refinement of site'
                               R 'riding-atom site attached to non-riding atom'
                               D 'distance or angle restraint on site'
                               T 'thermal displacement constraints'
                               U 'Uiso or Uij restraint (rigid bond)'
                               P 'partial occupancy constraint'
   _definition
;           A concatenated series of single-letter codes which indicate the
            refinement restraints or constraints applied to this site.  This
            item should not be used.  It has been replaced by
            _atom_site_refinement_flags_posn, _*_adp and *_occupancy.  It is
            retained in this dictionary only to provide compatibility with
            legacy CIFs
;

# STATUS: Preliminary approval 02-09-23

data_atom_site_refinement_flags_posn
    _name                      '_atom_site_refinement_flags_posn'
    _category                    atom_site
    _type                        char
    _list                        yes
    _list_reference            '_atom_site_label'
    loop_ _enumeration
          _enumeration_detail
                    . 'no constraints on positional coordinates'
                    D 'distance or angle restraint on positional coordinates'
                    G 'rigid group refinement of positional coordinates'
                    R 'riding-atom site attached to non-riding atom'
                    S 'special position constraint on positional coordinates'
                    DG   'combination of the above constraints'
                    DR   'combination of the above constraints'
                    DS   'combination of the above constraints'
                    GR   'combination of the above constraints'
                    GS   'combination of the above constraints'
                    RS   'combination of the above constraints'
                    DGR  'combination of the above constraints'
                    DGS  'combination of the above constraints'
                    DRS  'combination of the above constraints'
                    GRS  'combination of the above constraints'
                    DGRS 'combination of the above constraints'
    _definition
;              A code which indicates the refinement restraints or constraints
               applied to the positional coordinates of this site.
;
# STATUS: Preliminary approval 02-09-23

data_atom_site_refinement_flags_adp
    _name                      '_atom_site_refinement_flags_adp'
    _category                    atom_site
    _type                        char
    _list                        yes
    _list_reference            '_atom_site_label'
    loop_ _enumeration
          _enumeration_detail
          .  'no constraints on atomic displacement parameters'
          T   'special-position constraints on atomic displacement parameters' 
          U  'Uiso or Uij restraint (rigid bond)'
          TU 'Both constraints applied'
    _definition
;              A code which indicates the refinement restraints or constraints
               applied to the atomic displacement parameters of this site.
;
# COMMENT: Are these enumeration details clear?  What is the difference
# between these two flags?  Can both apply at the same time?
# STATUS: Preliminary approval 02-09-23

data_atom_site_refinement_flags_occupancy
    _name                      '_atom_site_refinement_flags_occupancy'
    _category                    atom_site
    _type                        char
    _list                        yes
    _list_reference            '_atom_site_label'
    loop_ _enumeration
          _enumeration_detail   . 'no constraints on site occupancy parameters'
                                P 'site occupancy constraint'
    _definition
;              A code which indicates that refinement restraints or
               constraints were applied to the occupancy of this site.
;
# STATUS: Preliminary approval 02-09-23

##################################################
#
#   ATOM SITES
#
##################################################

data_atom_sites_special_details
    _name               '_atom_sites_special_details'
    _category            atom_sites         
    _type                char
    _definition
;              Additional information about the atomic coordinates not coded
               elsewhere in the CIF.
;
# COMMENT: This could be useful in transcribing comments in databases.
# STATUS:  Preliminary approval 02-09-23


##################################################
#
#   CELL category
#
##################################################


data_cell_formula_units_Z_prime
    _name                      '_cell_formula_units_Z_prime'
    _category                    cell
    _type                        numb
    _enumeration_range           1:
    _definition
;              The number of the formula units as specified
               by _chemical_formula_structural, _chemical_formula_moiety or
               _chemical_formula_sum in the asymmetric unit of the
               unit cell given in the CELL category and the 
               space group defined in the SYMMETRY or SPACE GROUP category.
               This item is used to indicate the number of chemically
               equivalent molecules in the asymmetric unit.
;
# COMMENT: Requested by CCDC
# STATUS: Preliminary approval 2002-10-14

data_cell_reciprocal_angle_
    loop_ _name                '_cell_reciprocal_angle_alpha'
                               '_cell_reciprocal_angle_beta'
                               '_cell_reciprocal_angle_gamma'
    _category                   cell
    _type                       numb
    _type_conditions            esd
    _enumeration_range          0.0:180.0
    _enumeration_default        90.0
    _units                      deg
    _units_detail              'degrees'
    _definition
;              
     The angles defining the reciprocal cell.  These are related to 
     those in the real cell by:

cos(recip-alpha) = (cos(beta)*cos(gamma) - cos(alpha))/(sin(beta)*sin(gamma))

cos(recip-beta) = (cos(gamma)*cos(alpha) - cos(beta))/(sin(gamma)*sin(alpha))

cos(recip-gamma) = (cos(alpha)*cos(beta) - cos(gamma))/(sin(alpha)*sin(beta))

     (M.J.Buerger: X-ray Crystallography; New York, John Wiley & Sons Inc; 
     1942 p.360)
;
# COMMENT: Requested by CCDC
# STATUS: Preliminary approval 2002-10-14


data_cell_reciprocal_length_
    loop_ _name                '_cell_reciprocal_length_a'
                               '_cell_reciprocal_length_b'
                               '_cell_reciprocal_length_c'
    _category                   cell
    _type                       numb
    _type_conditions            esd
    _enumeration_range          0.0:
    _units                      A^-1^
    _units_detail              'reciprocal angstroms'
    _definition
;             
     The reciprocal cell lengths in inverse Angstroms.  These are 
     related to the real cell by the following equation:

     recip-a = b*c*sin(alpha)/V

     recip-b = c*a*sin(beta)/V

     recip-c = a*b*sin(gamma)/V

     where V is the cell volume.  (M.J.Buerger: X-ray Crystallography; 
     New York, John Wiley & Sons Inc; 1942 p.360)
;
# COMMENT: Requested by CCDC
# STATUS: Preliminary approval 2002-10-14

###################################################
#
#   CHEMICAL category
#
###################################################

# CHANGE TO AN EXISTING ITEM
#
# _chemical_melting_point should have added:
#
# _type_conditions  esd 
#

data_chemical_melting_point_
  loop_  _name                  '_chemical_melting_point_gt'
                                '_chemical_melting_point_lt'
    _category                   chemical
    _type                       numb
    _related_item               '_chemical_melting_point'
    _related_function           alternate
    _enumeration_range          0.0:
    _units                      K
    _units_detail              'Kelvins'
    _definition
;              A temperature in Kelvins below which (_*_lt) or above
               which (_*_gt) the melting point, the temperature at which a
               crystalline solid changes to a liquid, lies. These items allow a
               range of temperatures to be given.  _chemical_melting_point
               should always be used in preference to these items whenever
               possible.
;
# COMMENT: These item are introduced to allow for a maximum or minimum
# limit, or a range of temperatures to be given.  They are primarily designed
# to allow comments in exiting databases to be included in a CIF.
# STATUS: Preliminary approval 2002-10-14


data__chemical_properties_biological
    _name                      '_chemical_properties_biological'
    _category                   chemical
    _type                       char
   loop_    _example                   
;
    diverse biological activities including use as a 
    laxative and strong antibacterial activity against
    S. a ureus and weak activity against 
    cyclooxygenase-1 (COX-1)
;

;
    antibiotic activity against Bacillus subtilis 
    (ATCC 6051) but no significant activity against
    Candida albicans (ATCC 14053), Aspergillus flavus 
    (NRRL 6541) and Fusarium verticillioides (NRRL 25457)
;

;
    weakly potent lipoxygenase nonredox inhibitor
;

;
    no influenza A virus sialidase inhibitory and plaque 
    reduction activities
;

;
    low toxicity against Drosophila melanogaster
;

    _definition
;              A free description of the biological properties of the
               material.
;
# COMMENT: Suggested by CCDC for comments found in the CSD
# STATUS: Preliminary approval 2002-10-14

data_chemical_properties_physical
    _name                      '_chemical_properties_physical'
    _category                   chemical
    _type                       char
  loop_  _example                    
            air-sensitive
            moisture-sensitive 
            hygroscopic 
            deliquescent 
            oxygen-sensitive 
            photo-sensitive 
            pyrophoric
            semiconductor
            'ferromagnetic at low temperature'
            'paramagnetic and thermochromic'

    _definition
;              A free description of the physical properties of the material.
;
# COMMENT: Suggested by CCDC for comments found in the CSD
# STATUS: Preliminary approval 2002-10-14

data_chemical_temperature_decomposition
    _name                      '_chemical_temperature_decomposition'
   _category                    chemical
    _type                       numb
    _type_conditions            esd
    _units                      K
    _units_detail               Kelvin
    _example                    350
    _definition
;              The temperature in Kelvin at which a solid decomposes. 
;
# COMMENT: Suggested by CCDC.
# STATUS: Preliminary approval 2002-10-14

data_chemical_temperature_decomposition_*
    loop_ _name     '_chemical_temperature_decomposition_gt'
                    '_chemical_temperature_decomposition_lt'
    _category                   chemical
    _type                       numb
    _units                      K
    _units_detail               Kelvin
    _related_item               '_chemical_temperature_decomposition'
    _related_function           alternate
    _example                    350
    _definition
;             A temperature below which (_*_lt) or above which (_*_gt) the
              solid is known to decompose. These items allow a range of
              temperatures to be given. 
              _chemical_temperature_decomposition should always be used in
              preference to these items whenever possible.
;
# COMMENT: Suggested by CCDC.  
# STATUS: Preliminary approval 2002-10-14


data_chemical_temperature_sublimation
    _name                      '_chemical_temperature_sublimation'
   _category                    chemical
    _type                       numb
    _type_conditions            esd
    _units                      K
    _units_detail               Kelvin
    _example                    350
    _definition
;              The temperature in Kelvin at which a solid sublimes. 
;
# COMMENT: Suggested by CCDC.
# STATUS: Preliminary approval 2002-10-14

data_chemical_temperature_sublimation_*
    loop_ _name                 '_chemical_temperature_sublimation_gt'
                                '_chemical_temperature_sublimation_lt'
    _category                   chemical
    _type                       numb
    _units                      K
    _units_detail               Kelvin
    _related_item               '_chemical_temperature_sublimation'
    _related_function           Alternate
    _example                    350
    _definition
;             A temperature below which (_*_lt) of above which (_*_gt) the
              solid is known to sublime. 
              These items allow a range of temperatures to be given. 
              _chemical_temperature_sublimation should always be used in
              preference to these items whenever possible.
;
# COMMENT: Suggested by CCDC. 
# STATUS: Preliminary approval 2002-10-14


###################################################
#
#   CITATION category
#
###################################################

# The following item has already been approved but still needs to be
# incorporated into the dictionary.

data_citation_database_id_CSD
    _name                     '_citation_database_id_CSD'
    _category                  citation        
    _type                      char
    _list                      yes
    _list_reference           '_citation_id'
    _example                   LEKKUH
    _definition
;           Identifier ('refcode') of the database record in the Cambridge
            Structural Database containing details of the cited structure.
;
# COMMENT: Submitted by Brian McMahon
# STATUS: Approved 2001-12-03

####################################################
#
#   DATABASE Category
#
####################################################


data_database_code_depnum_ccdc_fiz
    _name                     '_database_code_depnum_ccdc_fiz'
    _category                  database
    _type                      char
    _definition
;              Deposition numbers assigned by the Fachinformatsionszentrum
               Karlsruhe (FIZ) to files containing structural information
               archived by the Cambridge Crystallographic Centre (CCDC)
;
# COMMENT: For use in the archives of CCDC.  Submitted by CCDC
# STATUS: Preliminary approval 2002-02-28

data_database_code_depnum_ccdc_journal
    _name                     '_database_code_depnum_ccdc_journal'
    _category                  database
    _type                      char
    _definition
;              Deposition numbers assigned by various journals to files
               containing structural information archived by the Cambridge
               Crystallographic Data Centre (CCDC)
;
# COMMENT: For use in the archives of CCDC.  Submitted by CCDC
# STATUS: Preliminary approval 2002-02-28

data_database_code_depnum_ccdc_archive
    _name                     '_database_code_depnum_ccdc_archive'
    _category                  database
    _type                      char
    _definition
;              Deposition numbers assigned by the Cambridge Crystallographic
               Data Centre (CCDC) to files containing structural information
               archived by the CCDC.
;

# COMMENT: For use in the archives of CCDC.  Submitted by CCDC
# STATUS: Preliminary approval 2002-02-28


data_database_CSD_history
    _name                     '_database_CSD_history'
    _category                  database        
    _type                      char
    _list                      yes
    _list_reference            ?
    _example                   ?
    _definition
;              A history of changes made by Cambridge Crystallographic Data
               Centre and incorporated into the Cambridge Structural Database
               (CSD).
;
# COMMENT: Requested by the CCDC
# STATUS: Preliminary approval 2002-11-11


###########################################
#
#   DIFFRN category
#
###########################################

data_diffrn_ambient_pressure_
    loop_    _name                      
                              '_diffrn_ambient_pressure_gt'
                              '_diffrn_ambient_pressure_lt'
    _category                  diffrn
    _type                      numb
    _type_conditions           esd
    _related_item              '_diffrn_ambient_pressure'
    _related_function          alternate
    _enumeration_range         0.0:
    _units                     kPa
    _units_detail             'kilopascals'
    _definition
;              The mean hydrostatic pressure in kilopascals above which
               (_*_gt) or below which (_*_lt) the intensities were measured.
               These items allow for a pressure range to be given.
               _diffrn_ambient_pressure should always be used in preference
               to these items whenever possible.
;
# COMMENT; Provides for a pressure range to be indicated.
# STATUS: Preliminary approval 2002-11-11

data_diffrn_ambient_temperature_
    loop_       _name                      
                              '_diffrn_ambient_temperature_gt'
                              '_diffrn_ambient_temperature_lt'
    _category                  diffrn
    _type                      numb
    _type_conditions           esd
    _related_item              '_diffrn_ambient_temperature'
    _related_function          alternate
    _enumeration_range         0.0:
    _units                     K
    _units_detail             'kelvins'
    _definition
;             The mean temperature in kelvins above which (_*_gt) or below
              which (_*_lt) the intensities were measured.  These items allow
              a range of temperatures to be given. 
              _diffrn_ambient_temperature should always be used in preference
              to these items whenever possible.
;
# COMMENT: Provides for a range of temperatures to be specified.
# STATUS: Preliminary approval 2002-11-11

################################################
#
#   DIFFRN_SOURCE
#
################################################

data_diffrn_source_take-off_angle
    _name                     '_diffrn_source_take-off_angle'
    _category                  diffrn_source
    _type                      numb
    _enumeration_range         0:90
    _units                     degrees
    _example                   1.53
    _definition
;              The complement of the angle between the normal to the surface
               of the X-ray tube target and the primary X-ray beam for beams
               generated by traditional X-ray tubes.
;
# COMMENT: Suggested by the powder DMG.
# 2003.06.26 Definition modified by BM 
# 2003-06-26 Definition further modified by Howard Flack
# STATUS: Preliminary approval 2002-11-11

######################################
#
#   DIFFRN_STANDARDS category
#
######################################

data_diffrn_standards_decay_%_lt
    _name                      '_diffrn_standards_decay_%_lt'
    _category                   diffrn_standards
    _type                       numb
    _related_item               '_diffrn_standards_decay_%'
    _related_function           alternate
    _enumeration_range          :100
    _definition
;              An upper limit on the percentage decrease in the mean
               intensity of the set of standard reflections measured at the
               start of the measurement of the diffraction pattern and at the
               end. This value is used when the decay is too small to be
               detected.
;
# COMMENT: Many experiments show no detectable decay and there is no provision
# for this at the moment other than to enter 0.0.
# STATUS: Preliminary approval 2002-11-11

#################################################
#
#  DIFFRN_REFLNS
#
#################################################

data_diffrn_reflns_measured_fraction_resolution_full
     _name                '_diffrn_reflns_measured_fraction_resolution_full'
     _category                  diffrn_reflns         
     _list                      yes
     _type                      numb
     _enumeration_range         0:1.0
     _related_item             '_diffrn_measured_fraction_theta_full'    
     _related_function          alternate
     _definition
;         Fraction of unique (symmetry-independent) reflections measured
          out to the resolution given in _diffrn_reflns_resolution_full.
          This number should be very close to 1.0, since it represents the
          fraction of reflections measured in the part of the diffraction
          pattern that is essentially complete.
;
# COMMENT: Replacement for _diffrn_measured_fraction_theta_full, moved to a
# more appropriate category and defined in terms of resolution rather than
# angle which depends on the radiation used.
# 2003-06-26 _related_function 'replace' changed to 'alternate'
# STATUS: Preliminary approval 2002-11-11

data__diffrn_reflns_measured_fraction_resolution_max
    _name                '_diffrn_reflns_measured_fraction_resolution_max'
    _category                   diffrn_reflns   
     _list                      yes
     _type                      numb
     _enumeration_range         0:1.0
    _related_item              '_diffrn_measured_fraction_theta_max'
    _related_function           alternate
     _definition
;         Fraction of unique (symmetry-independent) reflections measured
          out to the resolution given in _diffrn_reflns_resolution_max.
;
# COMMENT: Replacement for _diffrn_measured_fraction_theta_max, moved to a
# more appropriate category and defined in terms of resolution rather than
# angle which depends on the radiation used.
# 2003-06-26 _related_function 'replace' changed to 'alternate'
# STATUS: Preliminary approval 2002-11-11 

data_diffrn_reflns_resolution_full
    _name                      '_diffrn_reflns_resolution_full'
    _category                   diffrn_reflns
    _type                       numb
    _enumeration_range          0.0:
    _units                      A^-1^
    _units_detail              'reciprocal angstroms'
    _related_item              '_diffrn_reflns_theta_full'
    _related_function           alternate
    _definition
;              The resolution in reciprocal angstroms at which the measured 
               reflection count is close to complete. The fraction of unique
               reflections measured out to this resolution is given by         
               _diffrn_reflns_measured_fraction_resolution_full
;
# COMMENT: Replacement for _diffrn_reflns_theta_full expressed in terms of 
# resolution rather than an angle that depends on the radiation used.
# 2003-06-26 _related_function 'replace' changed to 'alternate'
# STATUS: Preliminary approval 2002-11-11

data_diffrn_reflns_resolution_max
    _name                      '_diffrn_reflns_resolution_max'
    _category                   diffrn_reflns
    _type                       numb
    _enumeration_range          0.0:
    _units                      A^-1^
    _units_detail              'reciprocal angstroms'
    _related_item              '_diffrn_reflns_theta_max'
    _related_function           alternate
    _definition
;              Maximum resolution of the measured diffraction pattern.
;
# COMMENT: Replacement for _diffrn_reflns_theta_max expressed in terms of 
# resolution rather than an angle that depends on the radiation used.
# 2003-06-26 _related_function 'replace' changed to 'alternate'
# STATUS: Preliminary approval 2002-11-11


#################################################
#
#  EXPTL_CRYSTAL
#
#################################################

#
# The following three items replace _exptl_crystal_colour, replacing the free
# description allowed there by a more structured colour description based on
# the standardized names adopted by the International Center for Diffraction
# Data.  This scheme allows for three standardized colour descriptors, each
# with its own enumeration list.
#
data_exptl_crystal_colour_primary
    _name                      '_exptl_crystal_colour_primary'
    _category                   exptl_crystal
    _type                       char
    _list                       both
    _list_reference            '_exptl_crystal_id'
    _related_item              '_exptl_crystal_colour'
    _related_function          alternate
    _definition
;             The enumeration list of standardized names developed for the
              International Center for Diffraction Data.
              The colour of a crystal is given by the combination of
              _exptl_crystal_colour_modifier with
              _exptl_crystal_colour_primary, as in 'dark-green', 
              'bluish-violet', if necessary combined with
              _exptl_crystal_colour_lustre, as in 'metallic-green'.
;
loop_ 
      _enumeration
        colourless              
        white                   
        black                   
        gray                    
        brown                   
        red                     
        pink                    
        orange                  
        yellow                  
        green                   
        blue                    
        violet                  

data_exptl_crystal_colour_modifier
    _name                      '_exptl_crystal_colour_modifier'
    _category                   exptl_crystal
    _type                       char
    _list                       both
    _list_reference            '_exptl_crystal_id'
    _related_item              '_exptl_crystal_colour'
    _related_function          alternate
    _definition
;             The enumeration list of standardized names developed for the
              International Center for Diffraction Data.
              The colour of a crystal is given by the combination of
              _exptl_crystal_colour_modifier with
              _exptl_crystal_colour_primary, as in 'dark-green', 
              'bluish-violet', if necessary combined with
              _exptl_crystal_colour_lustre, as in 'metallic-green'.
;

loop_
      _enumeration
          light           
          dark            
          whitish         
          blackish        
          grayish         
          brownish        
          reddish         
          pinkish         
          orangish        
          yellowish       
          greenish        
          bluish          

data_exptl_crystal_colour_lustre
    _name                      '_exptl_crystal_colour_lustre'
    _category                   exptl_crystal
    _type                       char
    _list                       both
    _list_reference            '_exptl_crystal_id'
    _related_item              '_exptl_crystal_colour'
    _related_function          alternate
    _definition
;             The enumeration list of standardized names developed for the
              International Center for Diffraction Data.
              The colour of a crystal is given by the combination of
              _exptl_crystal_colour_modifier with
              _exptl_crystal_colour_primary, as in 'dark-green', 
              'bluish-violet', if necessary combined with
              _exptl_crystal_colour_lustre, as in 'metallic-green'.
;
loop_
       _enumeration
             metallic         
             dull             
             clear            
#
# STATUS: Preliminary approval 2003-06-17 

data_exptl_crystal_density_meas_
    loop_    _name  
                               '_exptl_crystal_density_meas_gt'
                               '_exptl_crystal_density_meas_lt'
    _category                   exptl_crystal
    _type                       numb
    _type_conditions            esd
    _list                       both
    _list_reference            '_exptl_crystal_id'
    _enumeration_range          0.0:
    _units                      Mg^-3^
    _units_detail              'megagrams per cubic metre'
    _related_item              '_exptl_crystal_density_meas'
    _related_function          alternate
    _definition
;              The value above which (_*_gt) or below which (_*_lt) the
               density measured using standard chemical and physical
               methods lies. The units are megagrams per cubic metre (grams per
               cubic centimetre).  These items should not be used to report
               new experimental work where _exptl_crystal_density_meas should
               be used.  They are intended for use in reporting information in
               existing databases and archives which would be misleading if
               reported under _exptl_crystal_density_meas.
;
    loop_
     _example
     _example_detail
   '_exptl_crystal_density_meas_lt  1.0'       'specimen floats in water'

;     _exptl_crystal_density_meas_gt    2.5   
      _exptl_crystal_density_meas_lt    5.0
;

'Only the range within which the density lies was given in the original paper'
#
# STATUS: Preliminary approval 2003-06-16

data_exptl_crystal_density_meas_temp_*
    loop_
         _name                 '_exptl_crystal_density_meas_temp_gt'
                               '_exptl_crystal_density_meas_temp_lt'
    _category                   exptl_crystal
    _type                       numb
    _type_conditions            esd
    _list                       both
    _list_reference            '_exptl_crystal_id'
    _enumeration_range          0.0:
    _units                      K
    _units_detail              'Kelvins'
    _related_item              '_exptl_crystal_density_meas_temp'
    _related_function          alternate
    _definition
;              Temperature in kelvins above which (_*_gt) or below which
               (_*_lt) _exptl_crystal_density_meas was determined.  These
               items should not be used for reporting new work where the
               correct temperature of measurement should be given.  They are
               intended for use in reporting information stored in databases
               or archives which would be misleading if reported under
               _exptl_crystal_density_meas_temp.
;
loop_
       _example
       _example_detail
 '_exptl_crystal_density_meas_temp_lt   300'
;          The density was measured at some unspecified temperature below room 
           temperature.
;
# COMMENT: The above two items suggested by CCDC.
#
# STATUS: Preliminary approval 2003-06-16

data_exptl_crystal_recrystallization_method
    _name                      '_exptl_crystal_recrystallization_method'
    _category                   exptl_crystal        
    _type                       char
    _example                    ?
    _definition
;              Describes the method used to recrystallize the sample. 
               Sufficient details should be given for the procedure to be
               repeated.  The temperature or temperatures should be given as
               well as details of the solvent, flux or carrier gas with
               concentrations or pressures and ambient atmosphere.
;
# COMMENT: Suggested by CCDC.
# Definition elaborated to give details of what should be included.
# STATUS: Preliminary approval 2003-06-16



##########################################################
#
#    PUBL category
#
##########################################################

data_publ_contact_author_id_iucr
    _name                      '_publ_contact_author_id_iucr'
    _category                   publ        
    _type                       char    
    _list                       yes    
    _example                    2985
    _definition
;              Identifier in the IUCr contact database of the author
               submitting the manuscript and datablock.  This identifier may
               be available from the World Directory of Crystallographers
               (http://wdc.iucr.org).
;

# COMMENT: Submitted by Brian McMahon  This identifier will allow linking to
# other publications or files by the contact author. 
# (Linking based on name alone is inefficient because
# individuals change their names or spelling of the names.  A complementary
# data name is proposed for the authors in the PUBL_AUTHOR category.
# STATUS: Preliminary approval 2003-01-07 

#########################################################
#
#   PUBL_AUTHOR category
#
#########################################################

data_publ_author_id_iucr
    _name                      '_publ_author_id_iucr'
    _category                   publ_author
    _type                       char
    _list                       yes
    _example                    2985
    _definition
;              Identifier in the IUCr contact database of a publication
               author.  This identifier may be available from the World
               Directory of Crystallographers (http://wdc.iucr.org).
;

# COMMENT: Submitted by Brian McMahon.  See _publ_contact_author_id_iucr for
# further details.
# STATUS: Preliminary approval 2003-01-07 


#########################################
#
#   REFINE category     
#
#########################################


data_refine_ls_shift/su_max_lt
    _name                      '_refine_ls_shift/su_max_lt'
    _category                    refine
    _type                        numb
    _related_item              '_refine_ls_shift/su_max'
    _related_function            alternate
    _enumeration_range           0.0:
    _definition
;              An upper limit for the largest (ratio of the final
               least-squares parameter shift divided by the final 
               standard uncertainty).  This item is used when the largest
               value of the shift divided by the final standard uncertainty
               is too small to measure.
;
# STATUS: Preliminary approval 2003-01-07 

data_refine_ls_shift/su_mean_lt
    _name                      '_refine_ls_shift/su_mean_lt'
    _category                    refine
    _type                        numb
    _related_item              '_refine_ls_shift/su_mean'
    _related_function            alternate
    _enumeration_range           0.0:
    _definition
;              An upper limit for the average (ratio of the final
               least-squares parameter shift divided by the 
               final standard uncertainty).  This
               item is used when the average value of the shift divided by 
               the final standard uncertainty is too small to measure.
;
# STATUS: Preliminary approval 2003-01-07 


################################################
#
#           CATEGORY: SPACE_GROUP
#
################################################

data_SPACE_GROUP
    _name                  space_group
    _category              category_overview
    _type                  null
    _definition
;              Contains all the data items that refer to the space group as a
               whole, such as its name, crystal system etc.  It may be looped,
               for example, in a list of space groups and their properties.

               Only a subset of the space_group category items appear in the 
               core dictionary.  The remainder are found in the cif_sym
               dictionary.

               Space group types are identified by their International Tables
               for Crystallography Vol A number or Schoenflies symbol.  
               Specific settings of the space groups can be identified either
               by their Hall symbol or by specifying their symmetry operations.

               The commonly-used Hermann-Mauguin symbol determines the
               space group type uniquely but several different Hermann-Mauguin
               symbols may refer to the same space group type. It contains
               information on the choice of the basis, but not on the
               choice of origin.  Different formats for the Hermann_Mauguin
               symbol are found in the cif_sym dictionary.
;
    _example
;
           _space_group_id                 1
           _space_group_name_H-M_alt       'C 2/c'
           _space_group_IT_number          15
           _space_group_name_Hall          '-C 2yc'
           _space_group_crystal_system     monoclinic
;
# STATUS: Preliminary approval 2003-03-11
    

data_space_group_crystal_system
    _name              '_space_group_crystal_system'
    _category          space_group
    _list              both
    _list_mandatory    no
    _list_reference    '_space_group_id'
    _definition
;              The name of the system of geometric crystal classes of space
               groups (crystal system) to which the space group belongs.
               Note that rhombohedral space groups belong to the
               trigonal system.
;
    _type              char
     loop_
    _enumeration
                                  triclinic
                                  monoclinic
                                  orthorhombic
                                  tetragonal
                                  trigonal
                                  hexagonal
                                  cubic
# STATUS: Preliminary approval 2003-03-11

# 
# THE PREVIOUS ITEM REPLACES _symmetry_cell_setting.  The definition of the old
# item should be modified to make it clear that the old name is discontinued
# (the name is crystallographically incorrect and therefore misleading).  The
# following items should be added to the dictionary entry for
# _symmetry_cell_setting:
#
#    _related_item        '_space_group_crystal_system'
#    _related_function    replace
#
# Incidentally I have removed the _related_item and _related_function from the
# definition of _space_group_crystal_system because they are incorrect.  It is
# the _related_item that should 'replace' the item being defined, not the other
# way around.
#

    
data_space_group_id
    _name                '_space_group_id'
    _category            space_group
    _list                yes
    _list_mandatory      yes
    _definition
;              This is an identifier needed if _space_group_* items are looped.
;
    _type                char
     loop_
    _list_link_child
                         '_space_group_symop_sg_id'                

# STATUS: Preliminary approval 2003-03-11
    
data_space_group_IT_number
    _name                 '_space_group_IT_number'
    _category             space_group
    _list                 both
    _list_mandatory       no
    _list_reference       '_space_group_id'
    _definition
;              The number as assigned in International Tables for
               Crystallography Vol A, specifying the proper affine class (i.e.
               the orientation preserving affine class) of space groups
               (crystallographic space group type) to which the space group
               belongs.  This number defines the space group type but not
               the coordinate system in which it is expressed.
;
    _type                 numb
    _enumeration_range    1:230

#
# As above _symmetry_Int_Tables_number should have:
#
#   _related_item         '_space_group_IT_number'
#   _related_function     replace
#
# added, and the _related_item and _related_function lines should be removed
# from the cif_sym dictionary.
#
# STATUS: Preliminary approval 2003-03-11
    
data_space_group_name_Hall
    _name                 '_space_group_name_Hall'
    _category             space_group
    _list                 both
    _list_mandatory       no
    _list_reference       '_space_group_id'
     loop_
    _example
    _example_detail       'P 2c -2ac'            'Equivalent to Pca21'
                          '-I 4bd 2ab 3'         'Equivalent to Ia3d'
    _definition
;              Space group symbol defined by Hall (Acta Cryst. (1981) A37,
               517-525) (See also International Tables for Crystallography
               Vol.B (1993) 1.4 Appendix B). 
               Each component of the space group name is separated by a 
               space or an underscore.  The use of space is strongly
               recommended.  The underscore is only retained because it
               was used in earlier archived files.  It should not be 
               used in new CIFs. 
               _space_group_name_Hall uniquely defines the space group and
               its reference to a particular coordinate system.
;
    _type                 char

#
# As above '_symmetry_space_group_name_Hall' should have the following items
# added:
#
#   _related_item         '_space_group_name_Hall'
#   _related_function     replace
#
# and the _related_item and _related_function items should be removed
# from _space_group_name_Hall in the cif_sym dictionary.
#
# STATUS: Preliminary approval 2003-03-11

data_space_group_name_H-M_alt
    _name                  '_space_group_name_H-M_alt'
    _category               space_group
    _list                   both
    _list_mandatory         no
    _list_reference       '_space_group_id'
    _type                   char
     loop_
    _example
    _example_detail
;
     loop_
    _space_group_name_H-M_alt
     'C m c m' 
     'C 2/c 2/m 21/m' 
     'A m a m'        
;
'three examples for the space group number 63.'

    _definition
;              *_name_H-M_alt allows for any Hermann-Mauguin symbol
               to be given.  The way in which this item is used is determined
               by the user and in general is not intended to be interpreted by
               computer.  It may, for example, be
               used to give one of the extended Hermann-Mauguin symbols given
               in Table 4.3.1 of International Tables for Crystallography
               Vol A (1995) or a Hermann-Mauguin symbol for a conventional or
               unconventional setting.  
               Each component of the space group name is separated by a 
               space or underscore.  The use of space is strongly
               recommended.  The underscore is only retained because it
               was used in earlier archived files.  It should not be 
               used in new CIFs.  Subscripts should appear
               without special symbols. Bars should be given as negative
               signs before the numbers to which they apply. 

               The commonly
               used Hermann-Mauguin symbol determines the space group type
               uniquely but a given space group type may be described by
               more than one Hermann-Mauguin symbol. The space group type
               is best described using the *_IT_number or *_name_Schoenflies.
               The Hermann-Mauguin symbol may contain information on the
               choice of basis though not on the choice of origin. To
               define the setting uniquely use *_name_Hall or list the
               symmetry operations.
;

#
#  As above '_symmetry_space_group_name_H-M' should have the following items
# added:
#
#   _related_item      _space_group_name_H-M_alt
#    _related_function  replacement
#
# and the _related_item and _related_function should be removed from this item
# in the cif_sym dictionary.
#
# STATUS: Preliminary approval 2003-03-11

###########################################################
#
#     SPACE GROUP SYMOP
#
###########################################################

data_SPACE_GROUP_SYMOP
    _category                  category_overview
    _type                      null
    _definition
;              Contains information about the symmetry operations of the
               space group.
;
     loop_
    _example_detail
    _example
;
    The symmetry operations for the space group P21/c
;
;    loop_
    _space_group_symop_id
    _space_group_symop_operation_xyz
  1    x,y,z          
  2   -x,-y,-z        
  3   -x,1/2+y,1/2-z  
  4    x,1/2-y,1/2+z  
;
# STATUS: Preliminary approval 2003-03-11

data_space_group_symop_id
    _definition
;              An arbitrary identifier that uniquely labels each symmetry
               operation in the list.
;
    _type              char
    _name              '_space_group_symop_id'         
    _category          space_group_symop   
    _list              yes
    _list_mandatory    yes
#
# The following should be added to '_symmetry_equiv_pos_site_id' for the
# reasons described above:            
# 
#    _related_item      '_space_group_symop_id'
#    _related_function   replace
#
# and the _related_item and _related_function items should be removed from the
# cif_sym dictionary.
#

# STATUS: Preliminary approval 2003-03-11


data_space_group_symop_operation_xyz
    _name              '_space_group_symop_operation_xyz'
    _category          space_group_symop
    _list              both
    _list_mandatory    no
    _list_reference    '_space_group_symop_id'
     loop_
    _example
    _example_detail
              'x,1/2-y,1/2+z'  'c glide reflection through the plane (x,1/4,z)'
    _definition
;               A parsable string giving one of the symmetry operations of the
                space group in algebraic form.  If W is a matrix representation
                of the rotational part of the symmetry operation defined by the
                positions and signs of x, y and z, and w is a column of
                translations defined by the fractions, an equivalent position
                X' is generated from a given position X by the equation:

                          X' = WX + w

                (Note: X is used to represent bold_italics_x in International
                Tables for Crystallography Vol. A, Section 5)

                When a list of symmetry operations is given, it is assumed
                that the list contains all the operations of the space
                group (including the identity operation) as given by the
                representatives of the general position in International
                Tables for Crystallography Vol. A.
;
    _type              char
 
    _enumeration_default   'x,y,z'

# STATUS: Preliminary approval 2003-03-11
    
data_space_group_symop_sg_id
    _name              '_space_group_symop_sg_id'
    _category          space_group_symop
    _list              both
    _list_mandatory    no
    _list_reference    '_space_group_symop_id'
     loop_
    _example              
    _example_detail             
                          ?      ?
    _definition      
;              This must match a particular value of _space_group_id allowing
               the symmetry operation to be identified with a particular space
               group.
;
    _type              numb
    _list_link_parent  '_space_group_id'

# COMMENT: The _space_group items above have all been approved by
# COMCIFS. The only question we have to decide is which ones are to be included
# in the revised dictionary.  Some changes have been made in the descriptions
# and examples to make them more appropriate for the core dictionary.
#
# STATUS: Preliminary approval 2003-03-11

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