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Second round of proposed changes



Dear Colleagues,

     Having had no response to my message of Sept 9 opening
discussion on the proposed changes to the atom_site and
atom_sites categories of the core CIF dictionary, and in
accordance with the assumption spelled out in that message, these
proposals are unanimously approved by the Dictionary Maintenance
Group (DMG).  I have therefore marked these as approved in the
master list and we can now move us on to the next two categories:
cell and chemical.

     Please can I have some response, particularly from the
members of the DMG, so that I know that people are receiving and
reading this email?  Your silence will not be considered an
abstention but will be interpreted as a positive approval of the
changes.  If you have any reservations about these items, let me
know and I will remove them for further study.  Otherwise these
17 items will be added to the list of approved new (or modified)
datanames.

     Please respond by 14 October.

                         Best wishes

                              David


##################################################
#
#    PROPOSED NEW DEFINITIONS FOR CIF_CORE_2.3.DIC
#
##################################################
#
# Contents of this email
#
#     CELL
#        _cell_reciprocal_angle_alpha
#        _cell_reciprocal_angle_beta
#        _cell_reciprocal_angle_gamma
#        _cell_formula_units_Z
#        _cell_reciprocal_length_a
#        _cell_reciprocal_length_b
#        _cell_reciprocal_length_c
#     CHEMICAL
#        _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

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

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: Open for discussion


data_cell_formula_units_Z_prime
    _name                      '_cell_formula_units_Z'
    _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.
;
# COMMENT: Requested by CCDC
# STATUS: Open for discussion


data_cell_reciprocal_length_
    loop_ _name                '_cell_recirpocal_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: Open for discussion

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

data_chemical_melting_point_lt
    _name                      '_chemical_melting_point_lt'
    _category                   chemical
    _type                       numb
    _enumeration_range          0.0:
    _units                      K
    _units_detail              'Kelvins'
    _definition
;              A temperature in Kelvins which represents an upper limit to
               the melting point, the temperature at which a crystalline solid
               changes to a liquid.
;
# COMMENT: Introduced to allow for a maximum limit or range of temperatures to
# be given.
# Note that _chemical_melting_point should have the _type_conditions of 'esd'
# added
# STATUS: Open for discussion

data_chemical_melting_point_gt
    _name                      '_chemical_melting_point_gt'
    _category                   chemical
    _type                       numb
    _enumeration_range          0.0:
    _units                      K
    _units_detail              'Kelvins'
    _definition
;              A temperature in Kelvin which represents a lower limit to the
               melting point, the temperature at which a crystalline
               solid changes to a liquid.

;
# COMMENT:  See previous item
# STATUS: Open for discussion

data__chemcial_properties_biological
    _name                      '_chemcial_properties_biological'
    _category                   chemical
    _type                       char
    _example                    ?
    _definition
;              A free description of the biological properties of the
               material.
;
# COMMENT: Suggested by CCDC for comments found in the CSD
# STATUS: Open for discussion

data_chemcial_properties_physical
    _name                      '_chemcial_properties_physical'
    _category                   chemical
    _type                       char
    _example                    ?
    _definition
;              A free description of the physical properties of the material.
;
# COMMENT: Suggested by CCDC for comments found in the CSD
# STATUS: Open for discussion

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: Open for discussion

data_chemical_temperature_decomposition_*
    loop_ _name     '_chemical_temperature_decomposition_gt'
                    '_chemical_temperature_decomposition_lt'
    _category                   chemical
    _type                       numb
    _units                      K
    _units_detail               Kelvin
    _example                    350
    _definition
;             *_lt is a temperature below which the solid is known
              to decompose, *_gt is the a temperature above which
              the solid is known to decompose.
;
# COMMENT: Suggested by CCDC.  These two items allow a range of
# temperatures to be specified.
# STATUS: Open for discussion


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: Open for discussion

data_chemical_temperature_sublimation_*
    loop_ _name               '_chemical_temperature_sublimation_gt'
                              '_chemical_temperature_sublimation_lt'
    _category                   chemical
    _type                       numb
    _units                      K
    _units_detail               Kelvin
    _example                    350
    _definition
;             *_lt is a temperature below which the solid is known to
              sublime, *_gt is the a temperature above which the solid
              is known to sublime.
;
# COMMENT: Suggested by CCDC.  These two items allow a range of temperatures
# to be specified.
# STATUS: Open for discussion




*****************************************************
Dr.I.David Brown,  Professor Emeritus
Brockhouse Institute for Materials Research,
McMaster University, Hamilton, Ontario, Canada
Tel: 1-(905)-525-9140 ext 24710
Fax: 1-(905)-521-2773
idbrown@mcmaster.ca
*****************************************************


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