checkCIF procedure

PLAT413

 Short intermolecular H..H contacts may indicate incorrectly determined 
 structures (i.e. wrong symmetry, missed translation symmetry, wrong position   
 with reference to the symmetry elements, hydrogen atoms on atoms where there   
 should not be any  etc..). Short intermolecular contacts may be indicative 
 for inconsistent symmetry data (e.g. coordinates for space-group P43 and   
 symmetry specified as P41 or P21/n & P21/c confusions). 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.