checkCIF procedure

PLAT601

 Crystal structures in general do not contain large solvent accessible voids
 in the lattice. Most structures lose their long-range ordering when solvent
 molecules leave the crystal. Only when the remaining network is strongly   
 bonded (e.g. zeolites and some hydrogen bonded networks) the crystal   
 structure may survive. Residual voids in a structure may indicate the
 omission of (disordered) density from the model. Disordered density may go
 undetected when smeared since peak search programs are not designed to locate
 maxima on density ridges. The presence or absence of residual density in the
 void may be verified on a printed/plotted difference Fourier map or with
 PLATON/SQUEEZE. Voids of 40 Ang**3 may accommodate H2O. Small molecules such
 as Tetrahydrofuran have typical volumes in the 100 to 200 Ang**3 range. This
 test reports the volume of the largest solvent accessible void in the 
 structure. A paper reporting a crystal structure with a significant solvent 
 accessible void should at the least discuss the issue.