checkCIF procedure

PLAT163

 Missing or Zero s.u. (esd) on z-coordinate.
 Positional parameters for all non-hydrogen atoms in general positions are  
 checked for the presence of a non-zero s.u. on them. This includes 
 parameters fixed to fix the origin in polar space-groups (e.g. P41) which  
 is no longer necessary when refinement is done with modern programs
 (e.g. SHELXL, XTAL).