checkCIF procedure

PLAT372

 Large deviations from generally accepted values may indicate model problems,   
 over refinement etc. Default C2-C2 = 1.25 Ang. (X-Ray) value from  
 Ladd & Palmer, Structure Determination by Xray Crystallography (1985). 
 NOTE: C2-C2 indicates a bond between atoms with two bonds each. Conjugated
 systems may cause some 'false alarm' messages.