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Approval requested for symmetry dictionary



Dear COMCIFS

It is my pleasure to bring before you for your approval a new dictionary,
cif_sym.dic, containing categories and data names intended to carry
detailed information about crystallographic symmetry. If approved,
these items are candidates for superseding the existing small
symmetry-specific categories in the core dictionary.

This dictionary is expressed in a DDL2 formalism to facilitate integration
with the core dictionary as embedded in mmCIF; upon approval a DDL1
version will be derived from this suitable for mating with the DDL1 core.

This dictionary has been developed under the active supervision of David
Brown, and has already passed through several cycles of revision under 
the eyes of the COMCIFS Dictionary Review Committee.

Please review this dictionary and indicate your approval or reservations
before the end of June.

The dictionary accompanies this mail as an attachment and will also
be accessible from 1 June at the URL
http://www.iucr.org/iucr-top/cif/sym/cif_sym_0.9.dic

Regards
Brian
_______________________________________________________________________________
Brian McMahon                                             tel: +44 1244 342878
Research and Development Officer                          fax: +44 1244 314888
International Union of Crystallography                  e-mail:  bm@iucr.ac.uk
5 Abbey Square, Chester CH1 2HU, England                         bm@iucr.org
##########################################################
#
#  SYMMETRY CIF DICTIONARY
#
##########################################################
#
#  This dictionary is designed to provide the data names
#  required to describe crystallographic symmetry.
#
#  It is written in DDL2
#
#  This version, 0.09, is dated 2001-05-31
#
#  The categories and items defined in this version are:
#
#     space_group     (General information on the space group)
#         Bravais_type
#         centring_type
#         crystal_system
#         id                     (Parent to various .sg_id's)
#         Laue_class
#         IT_coordinate_system_code
#         IT_ number
#         name_Hall
#         name_H-M
#         name_H-M_alt
#         name_H-M_alt_description
#         name_H-M_full
#         name_Schoenflies
#         Patterson_name_H-M
#         point_group_H-M
#         reference_setting
#         transform_rotation_xyz
#         transform_origin_shift
#     space_group_symop               (Symmetry operators)
#         id                (parent to various .symop_id's)
#         generator_xyz
#         operation_description
#         operation_xyz
#         sg_id
#     space_group_Wyckoff   (Details of the Wyckoff positions)
#         coords_xyz
#         id    (parent to various .wyckoff_id's to be defined)
#         letter
#         multiplicity
#         sg_id
#         site_symmetry
#
##########################################################

data_cif_sym.dic

    _dictionary.title             'cif symmetry dictionary'
    _dictionary.version           0.09
    _dictionary.datablock_id      cif_sym.dic



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

save_SPACE_GROUP
    _category.id                  space_group
    _category.description
;              Contains all the data items that refer to the space group as a
               whole, such as its name, Laue group etc.  It may be looped, for
               example, in a list of space groups and their properties.

               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 by their Hall
               symbol, by specifying their symmetry operations or generators,
               or by giving the transformation that relates the specific setting
               to the reference setting based on International Tables for
               Crystallography Vol. A and stored in this dictionary.

               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.
;
    _category.mandatory_code      yes
    _category_examples.case
;
           _space_group.id                        1
           _space_group.name_H-M              C_2/c
           _space_group.name_Schoenflies      C2h^6
           _space_group.IT_number                15
           _space_group.name_Hall            -C_2yc
           _space_group.Bravais_type             mS
           _space_group.Laue_class              2/m
           _space_group.crystal_system   monoclinic
           _space_group.centring_type             C
           _space_group.Patterson_name_H-M    C_2/m
;
    _category_key.name          '_space_group.id'
     save_

#############################################


##############################################################################


save__space_group.bravais_type
    _item.name                  '_space_group.bravais_type'
    _item.category_id             space_group
    _item.mandatory_code          no
     loop_
    _item_examples.case
    _item_examples.detail         aP    'triclinic (anorthic) primitive lattice'
    _item_description.description
;              The symbol denoting the lattice type(Bravais type) to which the
               translational subgroup (vector lattice) of the space group
               belongs. It consisting of a lower case letter indicating the
               crystal system followed by an upper case letter indicating
               the lattice centring. The setting-independent symbol mS
               replaces the setting-dependent symbols mB and mC, and the
               setting-independent symbol oS replaces the setting-dependent
               symbols oA, oB and oC (see International Tables for
               Crystallography A 1995 edition p.13).
;
    _item_type.code                    char
     loop_
    _item_enumeration.value
     aP
     mP     mS
     oP     oS     oI    oF
     tP     tI
     hP     hR
     cP     cI     cF
     save_
#---------------------------------------------------

save__space_group.centring_type
    _item.name                  '_space_group.centring_type'
    _item.category_id             space_group
    _item.mandatory_code          no
    _item_description.description
;              Symbol for the lattice centring.  This symbol may be dependent
               on the coordinate system chosen.
;
    _item_type.code               char
     loop_
    _item_enumeration.value
    _item_enumeration.detail
          P     'primitive            no centring'
          A     'a face centred       (0,1/2,1/2)'
          B     'b face centred       (1/2,0,1/2)'
          C     'c face centred       (1/2,1/2,0)'
          F     'all faces centred    (0,1/2,1/2),(1/2,0,1/2),(1/2,1/2,0)'
          I     'body centred         (1/2,1/2,1/2)'
          R     'rhombohedral obverse centred (2/3,1/3,1/3),(1/3,2/3,2/3)'
          Rrev  'rhombohedral reverse centred (1/3,2/3,1/3),(2/3,1/3,2/3)'
          H     'hexagonal centred    (2/3,1/3,0),(1/3,2/3,0)'
     save_
#-----------------------------------------

save__space_group.crystal_system
    _item.name                  '_space_group.crystal_system'
    _item.category_id             space_group
    _item.mandatory_code          no
    _item_description.description
;              The name of the system of geometric crystal classes of space
               groups (crystal system) to which the space group belongs.
               Note that crystals with the hR lattice type belong to the
               trigonal system.
;
    _item_type.code               char
     loop_
    _item_enumeration.value
                                  triclinic
                                  monoclinic
                                  orthorhombic
                                  tetragonal
                                  trigonal
                                  hexagonal
                                  cubic
    _item_aliases.alias_name     '_symmetry_cell_setting'
    _item_aliases.dictionary      cif_core.dic
    _item_aliases.version         1.0
     save_
#--------------------------------------------------

save__space_group.id
     loop_
    _item.name
    _item.category_id
    _item.mandatory_code
               '_space_group.id'                 space_group             yes
               '_space_group_symop.sg_id'        space_group_symop       no
               '_space_group_Wyckoff.sg_id'      space_group_Wyckoff     no
    _item_description.description
;              This is an identifier needed if _space_group_* items are looped.
;
    _item_type.code               char
     loop_
    _item_linked.child_name
    _item_linked.parent_name
               '_space_group_symop.sg_id'                '_space_group.id'
               '_space_group_Wyckoff.sg_id'              '_space_group.id'
     save_
#------------------------------------------------

save__space_group.IT_coordinate_system_code
    _item.name                  '_space_group.IT_coordinate_system_code'
    _item.category_id             space_group
    _item.mandatory_code          no
    _item_description.description
;              A qualifier taken from the enumeration list identifying which
               setting in International Tables for Crystallography (3rd Edn)
               Vol. A (IT) is used.  See IT Table 4.3.1 Section 2.16,
               Table 2.16.1 Section 2.16.(i) and Fig. 2.6.4.  This item is
               not computer interpretable and cannot be used to define the
               coordinate system.  Use _space_group.transform_* instead.
;
    _item_type.code               char
     loop_
    _item_enumeration.value
    _item_enumeration.detail
               'b1'      'monoclinic unique axis b, cell choice 1, abc'
               'b2'      'monoclinic unique axis b, cell choice 2, abc'
               'b3'      'monoclinic unique axis b, cell choice 3, abc'
               '-b1'     'monoclinic unique axis b, cell choice 1, c-ba'
               '-b2'     'monoclinic unique axis b, cell choice 2, c-ba'
               '-b3'     'monoclinic unique axis b, cell choice 3, c-ba'
               'c1'      'monoclinic unique axis c, cell choice 1, abc'
               'c2'      'monoclinic unique axis c, cell choice 2, abc'
               'c3'      'monoclinic unique axis c, cell choice 3, abc'
               '-c1'     'monoclinic unique axis c, cell choice 1, ba-c'
               '-c2'     'monoclinic unique axis c, cell choice 2, ba-c'
               '-c3'     'monoclinic unique axis c, cell choice 3, ba-c'
               'a1'      'monoclinic unique axis a, cell choice 1, abc'
               'a2'      'monoclinic unique axis a, cell choice 2, abc'
               'a3'      'monoclinic unique axis a, cell choice 3, abc'
               '-a1'     'monoclinic unique axis a, cell choice 1, -acb'
               '-a2'     'monoclinic unique axis a, cell choice 2, -acb'
               '-a3'     'monoclinic unique axis a, cell choice 3, -acb'
               'abc'     'orthorhombic'
               'ba-c'    'orthorhombic'
               'cab'     'orthorhombic'
               '-cba'    'orthorhombic'
               'bca'     'orthorhombic'
               'a-cb'    'orthorhombic'
               '1abc'    'orthorhombic origin choice 1'
               '1ba-c'   'orthorhombic origin choice 1'
               '1cab'    'orthorhombic origin choice 1'
               '1-cba'   'orthorhombic origin choice 1'
               '1bca'    'orthorhombic origin choice 1'
               '1a-cb'   'orthorhombic origin choice 1'
               '2abc'    'orthorhombic origin choice 2'
               '2ba-c'   'orthorhombic origin choice 2'
               '2cab'    'orthorhombic origin choice 2'
               '2-cba'   'orthorhombic origin choice 2'
               '2bca'    'orthorhombic origin choice 2'
               '2a-cb'   'orthorhombic origin choice 2'
               '1'       'tetragonal or cubic origin choice 1'
               '2'       'tetragonal or cubic origin choice 2'
               'h'       'trigonal using hexagonal axes'
               'r'       'trigonal using rhombohedral axes'
     save_
#----------------------------------------------

save__space_group.IT_number
    _item.name                  '_space_group.IT_number'
    _item.category_id             space_group
    _item.mandatory_code          no
    _item_description.description
;              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.
;
    _item_type.code               numb
    _item_range.minimum           1
    _item_range.maximum           230
    _item_aliases.alias_name    '_symmetry_Int_Tables_number'
    _item_aliases.dictionary      cif_core.dic
    _item_aliases.version         1.0
     save_
#------------------------------------------------

save__space_group.laue_class
    _item.name                  '_space_group.Laue_class'
    _item.category_id             space_group
    _item.mandatory_code          no
     loop_
    _item_enumeration.value
               -1
               2/m  mmm
               4/m  4/mmm
               -3   -3m
               6/m  6/mmm
               m-3  m-3m
    _item_description.description
;              The Hermann-Mauguin symbol of the geometric crystal class of the
               point group of the space group where a center of inversion is
               added if not already present.

;
    _item_type.code               char
     save_
#-----------------------------------------------

save__space_group.name_hall
    _item.name                  '_space_group.name_Hall'
    _item.category_id             space_group
    _item.mandatory_code          no
     loop_
    _item_examples.case
    _item_examples.detail         'P 2c -2ac'            'Equivalent to Pca21'
                                  -I_4bd_2ab_3           'Equivalent to Ia3d'
    _item_description.description
;              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). A space or underline separates
               rotation symbols referring to different axes.
               _space_group.name_Hall uniquely defines the space group and
               its reference to a particular coordinate system.
;
    _item_type.code               char
    _item_aliases.alias_name     '_symmetry_space_group_name_Hall'
    _item_aliases.dictionary      cif_core.dic
    _item_aliases.version         1.0
     save_
#-------------------------------------------------

save__space_group.name_H-M
    _item.name                  '_space_group.name_H-M'
    _item.category_id             space_group
    _item.mandatory_code          no
     loop_
    _item_examples.case           'P 21/c'
                                  P21_c
                                  'P m n a'
                                  'P -1'
                                  F_m_-3_m
                                  P_63/m_m_m
    _item_description.description
;              The Short International Hermann-Mauguin space group symbol as
               defined on pp 14ff and given as the first item of each
               Space Group Table in Section 7 of International Tables
               for Crystallography Vol.A (1983). A space or underline
               separates each symbol referring to different axes.
               Subscripts should appear without special symbols. Bars
               should be given as negative signs before the numbers to which
               they apply.  The Short International Hermann-Mauguin symbol
               determines the space group type uniquely.  However, the space
               group type is better described using the *.IT_number or
               *.name_Schoenflies.  The Short International Hermann-Mauguin
               symbol contains no information on the choice of basis or
               origin. To define the setting uniquely use *.name_Hall, list
               the symmetry operations or generators, or give the
               transformation that relates the setting to the reference
               setting defined in this dictionary under *.reference_setting.
;
    _item_type.code               char
     loop_
    _item_related.related_name
    _item_related.function_code '_space_group.name_H-M_full'   alternate
                                '_space_group.name_H-M_alt'    alternate

    _item_aliases.alias_name     '_symmetry_space_group_name_H-M'
    _item_aliases.dictionary      cif_core.dic
    _item_aliases.version         1.0
     save_
#----------------------------------------------

save__space_group.name_H-M_alt
    _item.name                  '_space_group.name_H-M_alt'
    _item.category_id             space_group
    _item.mandatory_code          no
    _item_type.code               char
     loop_
    _item_examples.case
    _item_examples.detail
;
     loop_
    _space_group.name_H-M_alt
    _space_group.name_H-M_alt_description
     C_m_c_m(b_n_n)    'Extended Hermann-Mauguin symbol'
     'C 2/c 2/m 21/m'  'Full unconventional Hermann-Mauguin symbol'
;
'two examples for the space group number 63.'

    _item_description.description
;              *.name_H-M_alt allows for an alternative Hermann-Mauguin symbol
               to be given.  The way in which this item is used is determined
               by the user and should be described in the item
               _space_group.name_H-M_alt_description.  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 (1983) or a full Hermann-Mauguin symbol for an
               unconventional setting.  A space or underline separates each
               symbol referring to different axes. 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, list the
               symmetry operations or generators, or give the transformation
               that relates the setting to the reference setting defined
               in this dictionary under *.reference_setting.
;
     loop_
    _item_related.related_name
    _item_related.function_code '_space_group.name_H-M'           alternate
                                '_space_group.name_H-M_full'      alternate

    _item_aliases.alias_name     '_symmetry_space_group_name_H-M_alt'
    _item_aliases.dictionary      cif_core.dic
    _item_aliases.version         1.0

     save_
#---------------------------------------------------

save__space_group.name_H-M_alt_description
    _item.name                  '_space_group.name_H-M_alt_description'
    _item.category_id             space_group
    _item.mandatory_code          no
    _item_description.description
;              A free text description of the code appearing in
               _space_group.name_H-M_alt
;
    _item_type.code               char
     save_
#--------------------------------------------------

save__space_group.name_H-M_full
    _item.name                  '_space_group.name_H-M_full'
    _item.category_id             space_group
    _item.mandatory_code          no
     loop_
    _item_examples.case
    _item_examples.detail
               'P 21/n 21/m 21/a'      'full symbol for Pnma'
               P_21/n_21/m_21/a        'an alternative way of writing Pnma'
    _item_description.description
;              The Full International Hermann-Mauguin space group symbol as
               defined on pp 14ff and given as the second item of the second
               line of one of the Space Group Tables of Section 7 of
               International Tables for Crystallography Vol. A (1983). A space
               or underline separates each symbol referring to different axes.
               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 Full International Hermann-Mauguin
               symbol contains information about the choice of basis for
               monoclinic and orthorhombic space groups but does not give
               information about the choice of origin. To define the setting
               uniquely use *.name_Hall, list the symmetry operations
               or generators, or give the transformation relating
               the setting used to the reference setting defined in this
               dictionary under *.reference_setting.
;
    _item_type.code               char
     loop_
    _item_related.related_name
    _item_related.function_code '_space_group.name_H-M'             alternate
                                '_space_group.name_H-M_alt'         alternate
    _item_aliases.alias_name    '_symmetry_space_group_name_H-M_full'
    _item_aliases.dictionary      cif_core.dic
    _item_aliases.version         1.0
     save_
#-----------------------------------------------

save__space_group.name_Schoenflies
    _item.name                  '_space_group.name_Schoenflies'
    _item.category_id             space_group
    _item.mandatory_code          no
     loop_
    _item_examples.case
    _item_examples.detail
               'C2h^5'       'Schoenflies symbol for space group 14'
    _item_description.description
;              The Schoenflies symbol as listed in International Tables for
               Crystallography Vol. A denoting the proper affine class (i.e.
               orientation preserving affine class) of space groups (space group
               type) to which the space group belongs.  This symbol defines the
               space group type independently of the coordinate system in which
               the space group is expressed.

               The symbol is given in the form 'Schoenflies point group
               symbol' ^ 'superscript'.
;
    _item_type.code               char
     loop_
    _item_enumeration.value
               C1^1 Ci^1
               C2^1 C2^2 C2^3
               Cs^1 Cs^2 Cs^3 Cs^4
               C2h^1 C2h^2 C2h^3 C2h^4 C2h^5 C2h^6
               D2^1 D2^2 D2^3 D2^4 D2^5 D2^6 D2^7 D2^8 D2^9
               C2v^1 C2v^2 C2v^3 C2v^4 C2v^5 C2v^6 C2v^7 C2v^8 C2v^9 C2v^10
               C2v^11 C2v^12 C2v^13 C2v^14 C2v^15 C2v^16 C2v^17 C2v^18 C2v^19
               C2v^20 C2v^21 C2v^22
               D2h^1 D2h^2 D2h^3 D2h^4 D2h^5 D2h^6 D2h^7 D2h^8 D2h^9 D2h^10
               D2h^11 D2h^12 D2h^13 D2h^14 D2h^15 D2h^16 D2h^17 D2h^18 D2h^19
               D2h^20 D2h^21 D2h^22 D2h^23 D2h^24 D2h^25 D2h^26 D2h^27 D2h^28
               C4^1 C4^2 C4^3 C4^4 C4^5 C4^6
               S4^1 S4^2
               C4h^1 C4h^2 C4h^3 C4h^4 C4h^5 C4h^6
               D4^1 D4^2 D4^3 D4^4 D4^5 D4^6 D4^7 D4^8 D4^9 D4^10
               C4v^1 C4v^2 C4v^3 C4v^4 C4v^5 C4v^6 C4v^7 C4v^8 C4v^9 C4v^10
               C4v^11 C4v^12
               D2d^1 D2d^2 D2d^3 D2d^4 D2d^5 D2d^6 D2d^7 D2d^8 D2d^9 D2d^10
               D2d^11 D2d^12
               D4h^1 D4h^2 D4h^3 D4h^4 D4h^5 D4h^6 D4h^7 D4h^8 D4h^9 D4h^10
               D4h^11 D4h^12 D4h^13 D4h^14 D4h^15 D4h^16 D4h^17 D4h^18 D4h^19
               D4h^20
               C3^1 C3^2 C3^3 C3^4
               C3i^1 C3i^2
               D3^1 D3^2 D3^3 D3^4 D3^5 D3^6 D3^7
               C3v^1 C3v^2 C3v^3 C3v^4 C3v^5 C3v^6
               D3d^1 D3d^2 D3d^3 D3d^4 D3d^5 D3d^6
               C6^1 C6^2 C6^3 C6^4 C6^5 C6^6
               C3h^1
               C6h^1 C6h^2
               D6^1 D6^2 D6^3 D6^4 D6^5 D6^6
               C6v^1 C6v^2 C6v^3 C6v^4
               D3h^1 D3h^2 D3h^3 D3h^4
               D6h^1 D6h^2 D6h^3 D6h^4
               T^1 T^2 T^3 T^4 T^5
               Th^1 Th^2 Th^3 Th^4 Th^5 Th^6 Th^7
               O^1 O^2 O^3 O^4 O^5 O^6 O^7 O^8
               Td^1 Td^2 Td^3 Td^4 Td^5 Td^6
               Oh^1 Oh^2 Oh^3 Oh^4 Oh^5 Oh^6 Oh^7 Oh^8 Oh^9 Oh^10
     save_
#-----------------------------------------------

save__space_group.Patterson_name_H-M
    _item.name                  '_space_group.Patterson_name_H-M'
    _item.category_id             space_group
    _item.mandatory_code          no
     loop_
    _item_examples.case
               'P -1'
               'P 2/m'      'C 2/m'
               'P m m m'    'C m m m'   'I m m m'   'F m m m'
               'P 4/m'                  'I 4/m'
               'P 4/m m m'              'I 4/m m m'
               'P -3'       'R -3'
               'P -3 m 1'   'R -3 m'
               'P -3 1 m'
               'P 6/m'
               'P 6/m m m'
               'P m -3'                  'I m -3'    'F m -3'
               'P m -3 m'                'I m -3 m'  'F m -3 m'
    _item_description.description
;              The Hermann-Mauguin symbol of the type of that centrosymmetric
               symmorphic space group to which the Patterson function belongs,
               see International Tables for Crystallography Vol A Table 2.5.1.
               A space or underline separates each symbol referring to
               different axes. Subscripts should appear without special
               symbols.  Bars should be given as negative signs before
               the number to which they apply.
;
    _item_type.code               char
     save_
#------------------------------------------

save__space_group.point_group_H-M
    _item.name                  '_space_group.point_group_H-M'
    _item.category_id             space_group
    _item.mandatory_code          no
     loop_
    _item_examples.case           -4      4/m
    _item_description.description
;              The Hermann-Mauguin symbol denoting the geometric crystal
               class of space groups to which the space group belongs, and
               the geometric crystal class of point groups to which the
               point group of the space group belongs.
;
    _item_type.code               char
     save_
#-----------------------------------------


save__space_group.reference_setting
    _item.name                   '_space_group.reference_setting'
    _item.category_id              space_group
    _item.mandatory_code           no
    _item_description.description
;              The reference setting of a given space group is the setting
               chosen by the International Union of Crystallography as a
               unique setting to which other settings can be referred
               using the transformation matrix column pair given in
               *.transform_rotation_xyz and *.transform_origin_shift.

               The settings are given in the enumeration list in the form
               '_space_group.it_number':'_space_group.name_Hall'. The
               space group number defines the space group type and the
               Hall symbol specifies the symmetry generators referred to
               the reference coordinate system.

               The reference settings chosen are identical to those listed in
               International Tables for Crystallography Vol. A. For the cases
               where more than one setting is given, the following choices
               have been made.

               For monoclinic space groups: unique axis b and cell choice 1.

               For space groups with two origins: origin choice 2 (origin at
               inversion center indicated by adding :2 to the Hermann-Mauguin
               symbol in the enumeration list).

               For rhombohedral space groups: hexagonal axes (indicated by
               adding :h to the Hermann-Mauguin symbol in the enumeration list.

               (Based on http://xtal.crystal.uwa.edu.au/, (select 'Docs',
               select 'space-Group Symbols') Symmetry table of Ralf W.
               Grosse-Kunstleve, ETH, Zurich.)

               The enumeration list may be extracted from the dictionary
               and stored as a separate CIF that can be referred to as
               required.
;
    _item_type.code               char
     loop_
    _item_enumeration.value
    _item_enumeration.detail
               001:P_1             'C1^1   P_1'
               002:-P_1            'Ci^1   P_-1'
               003:P_2y            'C2^1   P_1_2_1'
               004:P_2yb           'C2^2   P_1_21_1'
               005:C_2y            'C2^3   C_1_2_1'
               006:P_-2y           'Cs^1   P_1_m_1'
               007:P_-2yc          'Cs^2   P_1_c_1'
               008:C_-2y           'Cs^3   C_1_m_1'
               009:C_-2yc          'Cs^4   C_1_c_1'
               010:-P_2y           'C2h^1  P_1_2/m_1'
               011:-P_2yb          'C2h^2  P_1_21/m_1'
               012:-C_2y           'C2h^3  C_1_2/m_1'
               013:-P_2yc          'C2h^4  P_1_2/c_1'
               014:-P_2ybc         'C2h^5  P_1_21/c_1'
               015:-C_2yc          'C2h^6  C_1_2/c_1'
               016:P_2_2           'D2^1   P_2_2_2'
               017:P_2c_2          'D2^2   P_2_2_21'
               018:P_2_2ab         'D2^3   P_21_21_2'
               019:P_2ac_2ab       'D2^4   P_21_21_21'
               020:C_2c_2          'D2^5   C_2_2_21'
               021:C_2_2           'D2^6   C_2_2_2'
               022:F_2_2           'D2^7   F_2_2_2'
               023:I_2_2           'D2^8   I_2_2_2'
               024:I_2b_2c         'D2^9   I_21_21_21'
               025:P_2_-2          'C2v^1  P_m_m_2'
               026:P_2c_-2         'C2v^2  P_m_c_21'
               027:P_2_-2c         'C2v^3  P_c_c_2'
               028:P_2_-2a         'C2v^4  P_m_a_2'
               029:P_2c_-2ac       'C2v^5  P_c_a_21'
               030:P_2_-2bc        'C2v^6  P_n_c_2'
               031:P_2ac_-2        'C2v^7  P_m_n_21'
               032:P_2_-2ab        'C2v^8  P_b_a_2'
               033:P_2c_-2n        'C2v^9  P_n_a_21'
               034:P_2_-2n         'C2v^10 P_n_n_2'
               035:C_2_-2          'C2v^11 C_m_m_2'
               036:C_2c_-2         'C2v^12 C_m_c_21'
               037:C_2_-2c         'C2v^13 C_c_c_2'
               038:A_2_-2          'C2v^14 A_m_m_2'
               039:A_2_-2b         'C2v^15 A_b_m_2'
               040:A_2_-2a         'C2v^16 A_m_a_2'
               041:A_2_-2ab        'C2v^17 A_b_a_2'
               042:F_2_-2          'C2v^18 F_m_m_2'
               043:F_2_-2d         'C2v^19 F_d_d_2'
               044:I_2_-2          'C2v^20 I_m_m_2'
               045:I_2_-2c         'C2v^21 I_b_a_2'
               046:I_2_-2a         'C2v^22 I_m_a_2'
               047:-P_2_2          'D2h^1  P_m_m_m'
               048:-P_2ab_2bc      'D2h^2  P_n_n_n:2'
               049:-P_2_2c         'D2h^3  P_c_c_m'
               050:-P_2ab_2b       'D2h^4  P_b_a_n:2'
               051:-P_2a_2a        'D2h^5  P_m_m_a'
               052:-P_2a_2bc       'D2h^6  P_n_n_a'
               053:-P_2ac_2        'D2h^7  P_m_n_a'
               054:-P_2a_2ac       'D2h^8  P_c_c_a'
               055:-P_2_2ab        'D2h^9  P_b_a_m'
               056:-P_2ab_2ac      'D2h^10 P_c_c_n'
               057:-P_2c_2b        'D2h^11 P_b_c_m'
               058:-P_2_2n         'D2h^12 P_n_n_m'
               059:-P_2ab_2a       'D2h^13 P_m_m_n:2'
               060:-P_2n_2ab       'D2h^14 P_b_c_n'
               061:-P_2ac_2ab      'D2h^15 P_b_c_a'
               062:-P_2ac_2n       'D2h^16 P_n_m_a'
               063:-C_2c_2         'D2h^17 C_m_c_m'
               064:-C_2ac_2        'D2h^18 C_m_c_a'
               065:-C_2_2          'D2h^19 C_m_m_m'
               066:-C_2_2c         'D2h^20 C_c_c_m'
               067:-C_2a_2         'D2h^21 C_m_m_a'
               068:-C_2a_2ac       'D2h^22 C_c_c_a:2'
               069:-F_2_2          'D2h^23 F_m_m_m'
               070:-F_2uv_2vw      'D2h^24 F_d_d_d:2'
               071:-I_2_2          'D2h^25 I_m_m_m'
               072:-I_2_2c         'D2h^26 I_b_a_m'
               073:-I_2b_2c        'D2h^27 I_b_c_a'
               074:-I_2b_2         'D2h^28 I_m_m_a'
               075:P_4             'C4^1   P_4'
               076:P_4w            'C4^2   P_41'
               077:P_4c            'C4^3   P_42'
               078:P_4cw           'C4^4   P_43'
               079:I_4             'C4^5   I_4'
               080:I_4bw           'C4^6   I_41'
               081:P_-4            'S4^1   P_-4'
               082:I_-4            'S4^2   I_-4'
               083:-P_4            'C4h^1  P_4/m'
               084:-P_4c           'C4h^2  P_42/m'
               085:-P_4a           'C4h^3  P_4/n:2'
               086:-P_4bc          'C4h^4  P_42/n:2'
               087:-I_4            'C4h^5  I_4/m'
               088:-I_4ad          'C4h^6  I_41/a:2'
               089:P_4_2           'D4^1   P_4_2_2'
               090:P_4ab_2ab       'D4^2   P_4_21_2'
               091:P_4w_2c         'D4^3   P_41_2_2'
               092:P_4abw_2nw      'D4^4   P_41_21_2'
               093:P_4c_2          'D4^5   P_42_2_2'
               094:P_4n_2n         'D4^6   P_42_21_2'
               095:P_4cw_2c        'D4^7   P_43_2_2'
               096:P_4nw_2abw      'D4^8   P_43_21_2'
               097:I_4_2           'D4^9   I_4_2_2'
               098:I_4bw_2bw       'D4^10  I_41_2_2'
               099:P_4_-2          'C4v^1  P_4_m_m'
               100:P_4_-2ab        'C4v^2  P_4_b_m'
               101:P_4c_-2c        'C4v^3  P_42_c_m'
               102:P_4n_-2n        'C4v^4  P_42_n_m'
               103:P_4_-2c         'C4v^5  P_4_c_c'
               104:P_4_-2n         'C4v^6  P_4_n_c'
               105:P_4c_-2         'C4v^7  P_42_m_c'
               106:P_4c_-2ab       'C4v^8  P_42_b_c'
               107:I_4_-2          'C4v^9  I_4_m_m'
               108:I_4_-2c         'C4v^10 I_4_c_m'
               109:I_4bw_-2        'C4v^11 I_41_m_d'
               110:I_4bw_-2c       'C4v^12 I_41_c_d'
               111:P_-4_2          'D2d^1  P_-4_2_m'
               112:P_-4_2c         'D2d^2  P_-4_2_c'
               113:P_-4_2ab        'D2d^3  P_-4_21_m'
               114:P_-4_2n         'D2d^4  P_-4_21_c'
               115:P_-4_-2         'D2d^5  P_-4_m_2'
               116:P_-4_-2c        'D2d^6  P_-4_c_2'
               117:P_-4_-2ab       'D2d^7  P_-4_b_2'
               118:P_-4_-2n        'D2d^8  P_-4_n_2'
               119:I_-4_-2         'D2d^9  I_-4_m_2'
               120:I_-4_-2c        'D2d^10 I_-4_c_2'
               121:I_-4_2          'D2d^11 I_-4_2_m'
               122:I_-4_2bw        'D2d^12 I_-4_2_d'
               123:-P_4_2          'D4h^1  P_4/m_m_m'
               124:-P_4_2c         'D4h^2  P_4/m_c_c'
               125:-P_4a_2b        'D4h^3  P_4/n_b_m:2'
               126:-P_4a_2bc       'D4h^4  P_4/n_n_c:2'
               127:-P_4_2ab        'D4h^5  P_4/m_b_m'
               128:-P_4_2n         'D4h^6  P_4/m_n_c'
               129:-P_4a_2a        'D4h^7  P_4/n_m_m:2'
               130:-P_4a_2ac       'D4h^8  P_4/n_c_c:2'
               131:-P_4c_2         'D4h^9  P_42/m_m_c'
               132:-P_4c_2c        'D4h^10 P_42/m_c_m'
               133:-P_4ac_2b       'D4h^11 P_42/n_b_c:2'
               134:-P_4ac_2bc      'D4h^12 P_42/n_n_m:2'
               135:-P_4c_2ab       'D4h^13 P_42/m_b_c'
               136:-P_4n_2n        'D4h^14 P_42/m_n_m'
               137:-P_4ac_2a       'D4h^15 P_42/n_m_c:2'
               138:-P_4ac_2ac      'D4h^16 P_42/n_c_m:2'
               139:-I_4_2          'D4h^17 I_4/m_m_m'
               140:-I_4_2c         'D4h^18 I_4/m_c_m'
               141:-I_4bd_2        'D4h^19 I_41/a_m_d:2'
               142:-I_4bd_2c       'D4h^20 I_41/a_c_d:2'
               143:P_3             'C3^1   P_3'
               144:P_31            'C3^2   P_31'
               145:P_32            'C3^3   P_32'
               146:R_3             'C3^4   R_3:h'
               147:-P_3            'C3i^1  P_-3'
               148:-R_3            'C3i^2  R_-3:h'
               149:P_3_2           'D3^1   P_3_1_2'
               150:P_3_2"          'D3^2   P_3_2_1'
               151:P_31_2_(0_0_4)  'D3^3   P_31_1_2'
               152:P_31_2"         'D3^4   P_31_2_1'
               153:P_32_2_(0_0_2)  'D3^5   P_32_1_2'
               154:P_32_2"         'D3^6   P_32_2_1'
               155:R_3_2"          'D3^7   R_3_2:h'
               156:P_3_-2"         'C3v^1  P_3_m_1'
               157:P_3_-2          'C3v^2  P_3_1_m'
               158:P_3_-2"c        'C3v^3  P_3_c_1'
               159:P_3_-2c         'C3v^4  P_3_1_c'
               160:R_3_-2"         'C3v^5  R_3_m:h'
               161:R_3_-2"c        'C3v^6  R_3_c:h'
               162:-P_3_2          'D3d^1  P_-3_1_m'
               163:-P_3_2c         'D3d^2  P_-3_1_c'
               164:-P_3_2"         'D3d^3  P_-3_m_1'
               165:-P_3_2"c        'D3d^4  P_-3_c_1'
               166:-R_3_2"         'D3d^5  R_-3_m:h'
               167:-R_3_2"c        'D3d^6  R_-3_c:h'
               168:P_6             'C6^1   P_6'
               169:P_61            'C6^2   P_61'
               170:P_65            'C6^3   P_65'
               171:P_62            'C6^4   P_62'
               172:P_64            'C6^5   P_64'
               173:P_6c            'C6^6   P_63'
               174:P_-6            'C3h^1  P_-6'
               175:-P_6            'C6h^1  P_6/m'
               176:-P_6c           'C6h^2  P_63/m'
               177:P_6_2           'D6^1   P_6_2_2'
               178:P_61_2_(0_0_5)  'D6^2   P_61_2_2'
               179:P_65_2_(0_0_1)  'D6^3   P_65_2_2'
               180:P_62_2_(0_0_4)  'D6^4   P_62_2_2'
               181:P_64_2_(0_0_2)  'D6^5   P_64_2_2'
               182:P_6c_2c         'D6^6   P_63_2_2'
               183:P_6_-2          'C6v^1  P_6_m_m'
               184:P_6_-2c         'C6v^2  P_6_c_c'
               185:P_6c_-2         'C6v^3  P_63_c_m'
               186:P_6c_-2c        'C6v^4  P_63_m_c'
               187:P_-6_2          'D3h^1  P_-6_m_2'
               188:P_-6c_2         'D3h^2  P_-6_c_2'
               189:P_-6_-2         'D3h^3  P_-6_2_m'
               190:P_-6c_-2c       'D3h^4  P_-6_2_c'
               191:-P_6_2          'D6h^1  P_6/m_m_m'
               192:-P_6_2c         'D6h^2  P_6/m_c_c'
               193:-P_6c_2         'D6h^3  P_63/m_c_m'
               194:-P_6c_2c        'D6h^4  P_63/m_m_c'
               195:P_2_2_3         'T^1    P_2_3'
               196:F_2_2_3         'T^2    F_2_3'
               197:I_2_2_3         'T^3    I_2_3'
               198:P_2ac_2ab_3     'T^4    P_21_3'
               199:I_2b_2c_3       'T^5    I_21_3'
               200:-P_2_2_3        'Th^1   P_m_-3'
               201:-P_2ab_2bc_3    'Th^2   P_n_-3:2'
               202:-F_2_2_3        'Th^3   F_m_-3'
               203:-F_2uv_2vw_3    'Th^4   F_d_-3:2'
               204:-I_2_2_3        'Th^5   I_m_-3'
               205:-P_2ac_2ab_3    'Th^6   P_a_-3'
               206:-I_2b_2c_3      'Th^7   I_a_-3'
               207:P_4_2_3         'O^1    P_4_3_2'
               208:P_4n_2_3        'O^2    P_42_3_2'
               209:F_4_2_3         'O^3    F_4_3_2'
               210:F_4d_2_3        'O^4    F_41_3_2'
               211:I_4_2_3         'O^5    I_4_3_2'
               212:P_4acd_2ab_3    'O^6    P_43_3_2'
               213:P_4bd_2ab_3     'O^7    P_41_3_2'
               214:I_4bd_2c_3      'O^8    I_41_3_2'
               215:P_-4_2_3        'Td^1   P_-4_3_m'
               216:F_-4_2_3        'Td^2   F_-4_3_m'
               217:I_-4_2_3        'Td^3   I_-4_3_m'
               218:P_-4n_2_3       'Td^4   P_-4_3_n'
               219:F_-4a_2_3       'Td^5   F_-4_3_c'
               220:I_-4bd_2c_3     'Td^6   I_-4_3_d'
               221:-P_4_2_3        'Oh^1   P_m_-3_m'
               222:-P_4a_2bc_3     'Oh^2   P_n_-3_n:2'
               223:-P_4n_2_3       'Oh^3   P_m_-3_n'
               224:-P_4bc_2bc_3    'Oh^4   P_n_-3_m:2'
               225:-F_4_2_3        'Oh^5   F_m_-3_m'
               226:-F_4a_2_3       'Oh^6   F_m_-3_c'
               227:-F_4vw_2vw_3    'Oh^7   F_d_-3_m:2'
               228:-F_4ud_2vw_3    'Oh^8   F_d_-3_c:2'
               229:-I_4_2_3        'Oh^9   I_m_-3_m'
               230:-I_4bd_2c_3     'Oh^10  I_a_-3_d'
     save_

save__space_group.transform_rotation_xyz
    _item.name                  '_space_group.transform_rotation_xyz'
    _item.category_id             space_group
    _item.mandatory_code          no
     loop_
    _item_examples.case
    _item_examples.detail
               'a,b-a,c'  'orthohexagonal to the reference hexagonal setting'
    _item_description.description
;              This item contains the (3x3) transformation P defined as follows:
               The relation between an arbitrary setting of a space group
               (basis vectors (a,b,c) origin O) and the reference coordinate
               system (basis vectors (a',b',c') origin O') is determined by
               an augmented affine (4x4) transformation matrix (cf. Section 5
               of International Tables for Crystallography, vol. A). It
               consists of (3x3) rotation matrix P=(Pij) which describes
               the transformation of the row (a,b,c)
               to the row of reference basis vectors (a',b',c'):

                    (a',b',c') = (a,b,c)P

               and the (3x1) column p=(pi1) which determines the origin
               shift of O with respect to reference origin O':

                    O' = O + p

               The rotation matrix P is given as:

                P11a+P21b+P31c, P12a+P22b+P32c, P13a+P23b+P33c.

               Note that the bases (a',b',c') and (a,b,c) are both written
               as rows. Thus, in each of the sums P11a+P21b+P31c,
               P12a+P22b+P32c, P13a+P23b+P33c, a column of P is listed.
               This way of presenting the matrix is different from the
               xyz presentation of the symmetry operations
               (cf. _space_group_symop.operation_xyz) where the matrices
               of the symmetry operations are listed by rows.

               The reference settings are enumerated under *.reference_setting.
;
    _item_type.code               char
     save_

save__space_group.transform_origin_shift
    _item.name                  '_space_group.transform_origin_shift'
    _item.category_id             space_group
    _item.mandatory_code          no
     loop_
    _item_examples.case
    _item_examples.detail         'a/2,b/2,0'     'origin shift p = (0.5,0.5,0)'
    _item_description.description
;              The origin shift vector, p, is defined as follows:
               The relation between an arbitrary setting of a space group
               (basis vectors (a,b,c) origin O) and the reference coordinate
               system (basis vectors (a',b',c') origin O') is determined by
               an augmented affine (4x4) transformation matrix (cf. Section 5
               of International Tables for Crystallography, vol. A). It
               consists of (3x3) rotation matrix P=(Pij) which describes
               the transformation of the row (a,b,c) to the row of
               reference basis vectors (a',b',c'):

                    (a',b',c') = (a,b,c)P

               and the (3x1) column p=(pi1) which determines the origin
               shift of O with respect to reference origin O':

                    O' = O + p

               The reference settings are enumerated under *.reference_setting
;
    _item_type.code               char
     save_

#####################################################
#
#    CATEGORY: SPACE_GROUP_SYMOP
#
#####################################################

save_SPACE_GROUP_SYMOP
    _category.id                  space_group_symop
    _category.description
;              Contains information about the symmetry operations of the
               space group.
;
    _category.mandatory_code      no
     loop_
    _category_examples.detail
    _category_examples.case
;
    The symmetry operations for the space group P21/c
;
;    loop_
    _space_group_symop.id
    _space_group_symop.operation_xyz
    _space_group_symop.operation_description
  1    x,y,z          'identity mapping'
  2    -x,-y,-z       'inversion'
  3    -x,1/2+y,1/2-z '2-fold screw rotation with axis in (0,y,1/4)'
  4    x,1/2-y,1/2+z  'c glide reflection through the plane (x,1/4,y)'
;
    _category_key.name          '_space_group_symop.id'
     save_
#####################################################

save__space_group_symop.generator_xyz
    _item.name                  '_space_group_symop.generator_xyz'
    _item.category_id             space_group_symop
    _item.mandatory_code          no
     loop_
    _item_examples.case
    _item_examples.detail
               'x,1/2-y,1/2+z'
;              c glide reflection through the plane (x,1/4,z) chosen as
               one of the generators of the space group
;
    _item_description.description
;              A parsable string giving one of the symmetry generators of the
               space group in algebraic form.  If W is a matrix representation
               of the rotational part of the generator 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 generators is given, it is assumed
               that the complete list of symmetry operations of the space
               group (including the identity operator) can be generated
               through repeated multiplication of the generators, that is,
               (W3, w3) is an operation of the space group if (W2,w2) and
               (W1,w1) (where (W1,w1) is applied first) are either operators
               or generators and:

                       W3 = W2 x W1
                       w3 = W2 x w1 + w2
;
    _item_type.code               char
    _item_default.value           'x,y,z'
     loop_
    _item_related.related_name
    _item_related.function_code '_space_group_symop.operation_xyz'   alternate
     save_
#-----------------------------------------

save__space_group_symop.id
    _item_description.description
;              An arbitrary identifier that uniquely labels each symmetry
               operation in the list.
;
    _item_type.code               char
     loop_
    _item.name
    _item.category_id
    _item.mandatory_code
               '_space_group_symop.id'         space_group_symop   yes
     loop_
    _item_aliases.alias_name
    _item_aliases.dictionary
    _item_aliases.version
               '_symmetry_equiv_pos_site_id'   cif_core.dic   1.0
               '_symmetry_equiv.id'            cif_mm.dic     1.0
     save_
#-----------------------------------------------

save__space_group_symop.operation_description
    _item.name                  '_space_group_symop.operation_description'
    _item.category_id             space_group_symop
    _item.mandatory_code          no
    _item_description.description
;              An optional text description of a particular symmetry operation
               of the space group.
;
    _item_type.code               char
     loop_
    _item_dependent.dependent_name
               '_space_group_symop.generator_xyz'
               '_space_group_symop.operation_xyz'
     save_
#------------------------------------------------

save__space_group_symop.operation_xyz
    _item.name                  '_space_group_symop.operation_xyz'
    _item.category_id             space_group_symop
    _item.mandatory_code          no
     loop_
    _item_examples.case
    _item_examples.detail
              'x,1/2-y,1/2+z'  'c glide reflection through the plane (x,1/4,z)'
    _item_description.description
;               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.
;
    _item_type.code               char
    _item_aliases.alias_name    '_symmetry_equiv_pos_as_xyz'
    _item_aliases.dictionary      cif_core.dic
    _item_aliases.version         1.0
    _item_default.value           'x,y,z'
     loop_
    _item_related.related_name
    _item_related.function_code '_space_group_symop.generator_xyz'    alternate
     save_
#------------------------------------------------

save__space_group_symop.sg_id
    _item.name                  '_space_group_symop.sg_id'
    _item.category_id             space_group_symop
    _item.mandatory_code          no
     loop_
    _item_example.case              
    _item_example.detail              
                                  ?      ?
    _item_description.description      
;               A child of _space_group.id allowing the symmetry operator
                to be identified with a particular space group.
;
    _item_type.code               numb
    _item_linked.child_name     '_space_group_symop.sg_id'    
    _item_linked.parent_name    '_space_group.id'
     save_



#####################################################
#
#    CATEGORY: SPACE_GROUP_WYCKOFF
#
#    Information about the Wyckoff positions
#
#
#####################################################

save_SPACE_GROUP_WYCKOFF
    _category.id                  space_group_Wyckoff
    _category.description
;              Contains information about Wyckoff positions of a space group.
               Only one site can be given for each special position but the
               remainder can be generated by applying the symmetry operations
               stored in _space_group_symop.operation_xyz.
;
    _category.mandatory_code      no
     loop_
    _category_examples.detail
    _category_examples.case
;
    This example is taken from the space group F_d_-3_c (number 228
    origin choice 2).  For brevity only a selection of special positions
    are listed.  The coordinates of only one site per special position can
    be given in this item, but coordinates of the other sites can be
    generated using the symmetry operations given in the SPACE_GROUP_SYMOP
    category.
;

;
     loop_
    _space_group_Wyckoff.id
    _space_group_Wyckoff.multiplicity
    _space_group_Wyckoff.letter
    _space_group_Wyckoff.site_symmetry
    _space_group_Wyckoff.coord_xyz
        1  192 h  1    x,y,z
        2   96 g  ..2  1/4,y,-y
        3   96 f  2..  x,1/8,1/8
        4   32 b  .32  1/4,1/4,1/4
;
    _category_key.name          '_space_group_Wyckoff.id'
     save_


save__space_group_Wyckoff.coords_xyz
    _item.name                  '_space_group_Wyckoff.coords_xyz'
    _item.category_id             space_group_Wyckoff
    _item.mandatory_code          no
     loop_
    _item_examples.case
    _item_examples.detail
               'x,1/2,0'     'Coordinates of a Wyckoff site with 2.. symmetry'
    _item_description.description
;              Coordinates of one site of a Wyckoff position expressed in
               terms of its fractional coordinates (x,y,z) in the unit cell.
               To generate the coordinates of all sites of this Wyckoff
               position it is necessary to multiply these coordinates by the
               symmetry operations stored in space_group_symop.operation_xyz.
;
    _item_type.code               char
    _item_default.value           'x,y,z'
     save_
#----------------------------------------

save__space_group_Wyckoff.id
     loop_
    _item.name
    _item.category_id
    _item.mandatory_code
               '_space_group_Wyckoff.id'     space_group_Wyckoff       yes
    _item_description.description
;              An arbitrary identifier that is unique to a particular Wyckoff
               position.
;
    _item_type.code               char
     save_
#---------------------------------------------

save__space_group_Wyckoff.letter
    _item.name                  '_space_group_Wyckoff.letter'
    _item.category_id             space_group_Wyckoff
    _item.mandatory_code          no
    _item_description.description
;              The Wyckoff letter as given in International Tables for
               Crystallography Vol. A associated with this position.
;
    _item_type.code               char
     loop_
    _item_enumeration.value
               a b c d e f g h i j k l m n o p q r s t u v w x y z \a
     save_
#-----------------------------------------------

save__space_group_Wyckoff.multiplicity
    _item.name                  '_space_group_Wyckoff.multiplicity'
    _item.category_id             space_group_Wyckoff
    _item.mandatory_code          no
    _item_description.description
;              The multiplicity of this Wyckoff position as given in
               International Tables Vol A.  It is the number of equivalent
               sites per conventional unit cell.
;
    _item_type.code               numb
    loop_
    _item_range.maximum
    _item_range.minimum           .   1
                                  1   1
    save_
#------------------------------------------------

save__space_group_Wyckoff.sg_id
    _item.name                  '_space_group_Wyckoff.sg_id'
    _item.category_id             space_group_Wyckoff
    _item.mandatory_code          no
     loop_
    _item_example.case              
    _item_example.detail              
     ?      ?
    _item_description.description      
;               A child of _space_group.id allowing the Wyckoff position
                to be identified with a particular space group.
;
    _item_type.code               char
    _item_linked.child_name     '_space_group_Wyckoff.sg_id'
    _item_linked.parent_name    '_space_group.id'
     save_
#------------------------------------------------

save__space_group_Wyckoff.site_symmetry
    _item.name                  '_space_group_Wyckoff.site_symmetry'
    _item.category_id             space_group_Wyckoff
    _item.mandatory_code          no
     loop_
    _item_examples.case
    _item_examples.detail
               2.22   'Position 2b in space group number 94, P_42_21_2'
               42.2   'Position 6b in space group number 222, P_n_-3_n'
               2..
;              Site symmetry for the Wyckoff position 96f in space group 228,
               F_d_-3_c.  The site symmetry group is isomorphic to the point
               group 2 with the 2-fold axis along one of the {100} directions.
;
    _item_description.description
;              The subgroup of the space group that leaves the point fixed.
               It is isomorphic to a subgroup of the point group of the
               space group. The site symmetry symbol indicates the symmetry
               in the symmetry direction determined by the Hermann-Mauguin
               symbol of the space group (see International Tables for
               Crystallography Vol A Section 2.12).
;
    _item_type.code               char
     save_
###################################################


##
     loop_
    _dictionary_history.version
    _dictionary_history.update
    _dictionary_history.revision
   0.01      1998-11-27
;                                (I.D.Brown)
   Creation of first draft of the dictionary.
   Contains the categories SPACE_GROUP, SPACE_GROUP_POS,
     SPACE_GROUP_REFLNS and SPACE_GROUP_COORD
;
   0.02      1999-02-15
;                                    (IDB)
   Changes made in response to suggestions from the project group.  New
   categories introduced
    SPACE_GROUP_SYMOP
    SPACE_GROUP_ASYM.
   The following category name changes were made:
    SPACE_GROUP_POS    to SPACE_GROUP_WYCKOFF
    SPACE_GROUP_REFLNS to SPACE_GROUP_WYCKOFF_CONDITIONS
    SPACE_GROUP_COORD  to SPACE_GROUP_WYCKOFF_COORD
   The items are arranged in alphabetical order
   Many other changes made in response to comments received
   including new data names for space group names
;
   0.03      1999-09-01
;  IDB
   Definitions of _space_group.IT_number, *.name_schoenflies
   *.Bravais_type, *point_group_H-M, *.crystal_system and *.Laue_class
   changed to those supplied by Litvin and Kopsky.
   *.setting_code changed to *.it_coordinate_system_code.
   *.name_H-M-K dropped.
   *.Patterson_symmetry_H-M changed to *.Patterson_name_H-M and
   enumeration list corrected.
   *.reference_setting added
   In category space_group_symop 'operator' changed to 'operation'.
    _space_group_symop.operation_matrix changed to conform to IT.
    _space_group_symop.generator_* added.
    _space_group.reference_setting added.
    _space_group_Wyckoff.* and related categories rewritten to avoid
   conflicting parent-child relations.  Removal of *_coord.* and addition
   of *_cond_link.*
;
   0.04      1999-11-01
;  IDB
   List of reference settings imported from Ralf Grosse-Kunstleve
   supplied 1999-10-29 by RWGK based on http://xtal.crystal.uwa.edu.au/
   (Select 'Docs', Select 'space Group Symbols') Symmetry table of Ralf
   W. Grosse-Kunstleve, ETH, Zuerich.
     version June 1995
          updated  September 29 1995
          updated  July       9 1997
     last updated  July      24 1998
   Matrices expanded into separate items for each element.
   References added for *_wyckoff.site_symmetry and
   *.IT_coordinate_system_code.
   *_asym category deleted.
   Numerous typographical errors corrected
;

   0.05      2000-01-12
;  IDB
   Further clarifications to definitions as suggested by Aroyo,
   Wondratschek, Madariaga, Litvin and Grosse-Kunstleve.
   Removal of all matrix forms of matrices (leaving xyz form) in the hope
   that a new DDL will make matrix representation simpler.
   Removal of *_Wyckoff_cond and *_Wyckoff_cond_link categories until a
   new DDL simplifies their structure.
   Added _space_group.transform_* items
;
   0.06      2000-05-04
;  IDB
   Further clarification of definitions as suggested by Aroyo,
   Wondratschek, Madariaga and Grosse-Kunstleve, particularly
   clarification of the Hermann-Mauguin symbols and Bravais types and
   changes to conform to the usage of ITA.
;
   0.07      2000-07-18
;  IDB
   Further clarifications and corrections from Wondratschek and
   Grosse-Kunstleve.  Dictionary checked in vcif.

   Brian McMahon:
   Structural review for COMCIFS. Some reformatting and cleaning up of
   minor typos. Checked against vcif and cyclops.

;
   0.08      2000-07-20
;  J. Westbrook

   Miscellaneous corrections and reformatting from software scan.
;
   0.09      2001-05-31
;  IDB
   The links between the space_group category and the
   space_group_symop and space_group_Wyckoff categories are
   corrected as well as the links between space_group_symop and the
   various geom_ categories.

   Brian McMahon:
   Changed type of _space_group_symop.sg_id to numb at request of IDB.
;

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