checkCIF procedure

PLAT971

 A Larger than expected residual density maximum outside a heavy atom (metal)
 location is detected in an independently calculated difference density map
 (using the IAM model). Its distance to the heavy atom is typically at around
 0.9 Ang. It is typically related to inadequate correction for absorption. 
 Face indexing based correction might be needed for high mu * r samples. It 
 might also be caused by unaccounted for twinning, disorder, wrongly assigned
 atom types, wrong symmetry, unaccounted for solvent and other model errors.