CheckCIF-SYMMG01

PROC-NAME: SYMMG01 Type_1

PURPOSE: To check that the _symmetry_space_group_name_H-M value is recognised as a legitimate symmetry symbol.

PROCEDURE:

(1) ATTACH list of H-M symbols, in all settings (e.g. 'symmap' STAR-format file of R Grosse-Kunstleve)

(2) SEARCH for a match of _symmetry_space_group_name_H-M with an entry in the list.

(3) EXTRACT the space group number of the matched symbol.

(4) EXTRACT the number of symmetry equivalent positions.

TEST

IF (2) fails, issue ALERT A that symbol unrecognied.

   "Alert A Unrecognised _symmetry_space_group_name_H-M"

IF the number from (3) != _symmetry_space_group_number,

issue an ALERT A of mismatch.

   "Alert A _symmetry_space_group_number does not match H-M symbol"

The space group symbol given under _symmetry_space_group_name_H-M is missing, or it cannot be recognised and/or does not correspond with the space group number given under symmetry_space_group_number.

Note that this message usually means that you have incorrectly formatted the space group symbol. Do not insert subscript formatting or parentheses in the space group symbol. 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.

(http://journals.iucr.org/services/cif/checking/SYMMG_01.html)

例：SYMMG01_ALERT_1_A _symmetry_space_group_number does not match H-M symbol

From the CIF: _space_group_IT_number ÿÿÿÿ

From the CIF: _symmetry_space_group_name_H-M Cc

Int. Tables space group number for Cc is 9

警告原因：出现这个警告是因为报道的空间群与检测的空间群不一致。原因可能是解析时做过空间群变换，而填写的时候是直接从PCF文件中复制到CIF文件中的。PCF文件是变换空间群之前的信息。

解决策略：将检测得到的正确空间群填入CIF中即可。