Packing efficiency of coordination polyhedra

Abstract

Close-packing of hard spheres is a general structural stability criterion for alloy phases. This paper aims at explaining the close-packing geometries of coordination polyhedral clusters composed of non-equivalent spheres. The shell atoms are separately treated according to their site symmetries. Ideal close-packing curves as functions of atomic radius ratios between the central atom and the shell atoms have to be introduced to evaluate the packing efficiencies of the clusters with coordination numbers CN = 9–11, where the shell atoms are located at least at two non-equivalent sites. Close-packing features of clusters involved in amorphous alloys are confirmed.