menucheckCIF procedure
PROC-NAME: REFLT02 Type_1PURPOSE: To check that _reflns_number_total is greater than or equal to the _reflns_number_gt.
PROCEDURE:
TEST
IF _reflns_number_total < _reflns_number_gt
issue ALERT B
"Alert B The number of reflections greater than the sigma threshold cannot exceed the number of symmetry-independent reflections"
|
The total number of symmetry-unique reflections, including all
reflections considered to be "unobserved", but excluding
systematically absent reflections, should be given under
_reflns_number_total. If Friedel-related reflections are being
treated as independent observations in order to utilise the effects
of anomalous dispersion, _reflns_number_total should correspond
with the total number of these independent reflections.
Normally, one uses just these independent reflections
during refinement and any subsequent set of reflections derived from
this must, logically, be a subset of the total unique reflections.
Therefore, the reported number of reflections for _reflns_number_gt,
i.e. those with intensity greater than the sigma threshold defined by
_reflns_threshold_expression, must normally be less than (or possibly
equal to) the number given under _reflns_number_total.
Check for typographical errors and/or that you have merged the equivalent reflections correctly before refinement. An exception to this requirement may occur if data from a non-merohedrally twinned crystal is employed, as this may result in more than one entry in the reflection file for a given set of h,k,l indices (e.g. data read into SHELXL with HKLF 5). As a result, more reflections may be used in the refinement than the apparent number of unique reflections. A second exception might be if you deliberately choose not to merge symmetry equivalent reflections before the refinement. This procedure is not recommended and its use should be specifically mentioned under _publ_section_exptl_refinement. |
"_reflns_number_observed is an old dataname which has been superceded by _reflns_number_gt"
| You are using an "old-fashioned", but still legal data name: _reflns_number_observed. Please update the item to match the currently preferred name of _reflns_number_gt. To ease this problem for the future, it is recommended that you upgrade or modify your CIF generating software accordingly. |
