checkCIF procedure

PLAT420

 Potential hydrogen bond donors are checked for the presence of suitable
 acceptors using commonly used (Jeffrey) H-bond criteria. As a general rule 
 there should be an acceptor for each donor. Exceptions are very rare for O-H   
 and more common for -NH and -NH2. A common error is an -OH with Hydrogen atom
 on a calculated position with O-H pointing in the wrong direction.