checkCIF procedure

PLAT234

 The components of the anisotropic displacement parameters along chemical   
 bonds are assumed to be equal in magnitude. Large differences might
 indicate contamination of these parameters with other (unresolved) effects 
 such as (substitutional) disorder, model or data errors and/or 
 over-refinement. Atomic sites assigned the wrong scattering type (e.g. Ag  
 versus Br) should generate 'problem signals' with this test. Data sets 
 corrected for absorption effects with DELREF techniques (e.g. DIFABS, SHELXA,  
 XABS2) often show large DELU values for bonds involving the heaviest atom. 
 Note: The original 'Hirshfeld-test' was defined in absolute terms (see 
 F.L. Hirshfeld, Acta Cryst. (1976). A32, 239-244).