checkCIF procedure

PLAT701

 Bond distances given in the CIF are cross-checked with corresponding   
 values calculated from the coordinates.  Alerts are set at 1,2 and 3 Sigma 
 deviation levels.  
 NOTE: Default s.u.'s are used where no s.u. given (e.g. for C-H). In general,
 all differences should be within the associated s.u. Small differences may
 arise from rounding. Very large deviation (or zero distance) normally
 indicate incorrectly specified symmetry operations on the associated atoms,
 or 'cut-and-pasting' of incompatible CIF's.