Methods for Assessing the Degree of Sphericity
of Molecules and a Study of Molecular Shapes
in the Structure of Binary Inorganic Compounds

E. V. Peresypkina and V. A. Blatov

Samara State University, ul. Akademika Pavlova 1, Samara, 443011 Russia

Received May 28, 2002

Abstract—Several geometric criteria for estimating the degree of deviation of the molecular shape from a per-
fect sphere have been tested. The most universal molecular-sphericity parameter, which is applicable to mole-
cules of arbitrary composition and explicitly takes into account the shape of a molecule, is the reduced value of
the dimensionless normalized second moment of the molecular Voronoi–Dirichlet polyhedron (mol). Based
on 125 crystal structures of binary molecular inorganic compounds, correlations between sphericity parameters
and physicochemical factors that influence the shape of a molecule, such as molecular geometry, the strength
of intermolecular interactions, specific features of the mutual influence of atoms in a molecule, and thermal
polymorphism, have been established.

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