checkCIF procedure

PLAT430

 This test alerts for possibly missed Hydrogen bonds as indicated by short  
 (i.e. shorter than sum of the van der Waals radii - 0.2 Angstrom)  
 Donor - Acceptor atom distances.
 NOTE: Short C=O .. O=C are observed sometimes when part of three-centre
 O-H, N-H or C-H O..O bridging.