checkCIF procedure

PLAT412

 Short intramolecular contacts may arise when H-atoms are in (false)
 calculated positions. Short intramolecular contacts may also be a sign for a   
 false structure with the molecule sitting on a site with improper site 
 symmetry (e.g. '2' instead of '-1') which may happen when a lattice
 translation is missed. Short contacts are defined using a van der Waals
 radius of 1.2 Angstrom. Short H .. H contact involving CH3 H-atoms are often   
 hampered by the fact that they involve H atoms at not optimal calculated   
 positions.