Pseudosymmetry in Trinitropyrazole: The Cost of Error in Space‐Group Determination

Abstract

electron density distribution · pseudosymmetry · space groups · structure elucidation · X-ray diffraction With more than 9 % of crystal structures having several independent species (Z' > 1) in an asymmetric unit [1] (with the number of examples increasing over the years [2] ) and 27 % of them showing approximate symmetry elements, [3] the pseudosymmetry phenomenon has become a widely recognized disaster in the solid-state world that significantly complicates the scientific efforts of many chemists and crystallographers. [4,5] Although there were episodes of its successful use, [6,7] pseudosymmetry is responsible for many failures to correctly deduce the crystal structure of a chemical substance. Moreover, this occurs more frequently than is often recognized, [5] thus causing the "wrong" structures to regularly appear in the literature. [8]