checkCIF procedure

PLAT360

 Large deviations from generally accepted values may indicate model problems,   
 over refinement etc. Default C4-C4 = 1.54 Ang. (X-Ray) value from  
 Ladd & Palmer, Structure Determination by Xray Crystallography (1985). 
 NOTE: C4-C4 indicates a bond between atoms with 4 bonds each.