SYMMG02

PROC-NAME: SYMMG02 Type_1

PURPOSE: To check that the _symmetry_space_group_name_H-M given is consistent with the _symmetry_equiv_pos_as_xyz if given.

PROCEDURE:
(1). Search the symmap file to produce a Hall symbol from the H-M symbol. Generate the xyz from this and convert back into a H-M symbol via the Hall symbol and symmap file.
(2). Generate a H-M symbol from the xyz via the Hall symbol and symmap file.
(3). xcheck the H-M symbols generated from (1) and (2).
SUMMARY:
h-m --> (symmap) --> hall --> xyz --> hall --> (symmap) --> h-m
hall --> xyz --> hall --> (symmap) --> h-m
xyz --> hall --> (symmap) --> h-m

IF h-m and hall are inconsistent issue ALERT A
   "Alert A The _symmetry_equiv_pos_as_xyz values are in consistent with the H-M symbol given"

IF the number of _symmetry_equiv_pos_as_xyz positions does not match the number expected for the given space group issue ALERT A
   "Alert A The number of _symmetry_equiv_pos_as_xyz positions in the CIF does not match the number expected for this space group"

IF _symmetry_equiv_pos_as_xyz loop is not present issue ALERT A
   "Alert A _symmetry_equiv_pos_as_xyz not in the CIF"

IF _symmetry_equiv_pos_as_xyz loop is incorrectly formatted issue ALERT B
with an appropriate message, e.g.
   "Alert B The denominator for a fractional translation has been omitted."
   "Alert B More than one identity symop (x,y,z) detected."
etc,.....

The space group symbol given under _symmetry_space_group_name_H-M cannot be matched with the space group symmetry operators given under _symmetry_equiv_pos_as_xyz.

Check that you have fully and correctly specified and formatted both _symmetry_space_group_name_H-M and _symmetry_equiv_pos_as_xyz and that they both refer to the SAME space group and the SAME setting of the axes.

_symmetry_equiv_pos_as_xyz must include ALL symmetry operators for the space group concerned, including the identity x,y,z, all those related by a centre of inversion and all those related by a non-primitive lattice operation.

Example:
loop_
_symmetry_equiv_pos_as_xyz
   'x, y, z'
   '-x, y+1/2, -z+1/2'
   '-x, -y, -z'
   'x, -y+1/2, z+1/2'

The space group symbol must not include subscript formatting or parentheses. You must leave spaces between symbols referring to different axes.

Examples for _symmetry_space_group_name_H-M:

Correct Incorrect

'P 21 21 21' 'P2~1~2~1~2~1~' or 'P212121'

'P 1 21/c 1' ['P21/c' allowed, but]
[not strictly correct] 'P2(1)/c'

'P 2/n 2/n 2/n (origin at -1)'

'R -3 2/m'

Note that the H-M symbol does not necessarily contain complete information about the symmetry and the space-group origin. If used always supply the FULL symbol from International Tables for Crystallography, Vol. A (1992) and indicate the origin and the setting if it is not implicit. If there is any doubt that the equivalent positions can be uniquely deduced from this symbol specify the _symmetry_equiv_pos_as_xyz *_Hall data items as well.

Full list of validation algorithms