checkCIF procedure

PLAT076

 The CIF contains an atom sitting on a special position with occupancy  
 specified as less than 1.0. This is often an error and the result of the   
 confusion of the notions 'occupancy' and 'population parameter'. The first 
 should be 1.0 for a fully occupied site. The latter multiplies the 
 site-symmetry with the occupancy. Thus, for a fully occupied site on a 
 mirror plane the site-symmetry will be 0.5 * 1.0 = 0.5.
 NOTE: A wrong occupancy number will lead to an incorrect expected chemical
 formula.