checkCIF procedure

PROC-NAME: RINTA01 Type_3

PURPOSE: To check that _diffrn_reflns_av_R_equivalents is within expected limits.

PROCEDURE:
TEST
IF _diffrn_reflns_av_R_equivalents > 0.20 issue ALERT A
   "Alert A The value of Rint is greater than 0.20"
> 0.15 issue ALERT B
   "Alert B The value of Rint is greater than 0.15"
> 0.10 issue ALERT C
   "Alert C The value of Rint is greater than 0.10"
< 0.0 issue ALERT A
   "Alert A The value of Rint is less than 0.0"

The value of _diffrn_reflns_av_R_equivalents should normally be considerably less than 0.10. Higher values should be accompanied by a suitable explanation in the _publ_section_exptl_refinement section. However, authors should first ensure that there are not overlooked problems associated with the data or the space group. Elevated values for _diffrn_reflns_av_R_equivalents may be indicative of a need to recollect the data from a crystal of higher quality or that there is a problem with the data treatment. Consider the following: (a) The absorption corrections are inadequate or inappropriate. (b) The overall quality of the data may be poor due to the crystal quality. (c) The crystal is very weakly diffracting, so that a large proportion of essentially "unobserved" reflections are being used in the refinement. You should consider using a better crystal or a data collection at low temperature and/or, if the compound is organic, using Cu radiation. (d) You are working in the wrong crystal system or Laue group. (e) You have only a very small number of equivalent reflections, which may lead to artificially high values of _diffrn_reflns_av_R_equivalents Note that if _diffrn_reflns_av_sigmaI/netI is also large, the quality of the data should be considered to be suspect.