Statistical geometry of molten alkali halides

Abstract

The generalized Dirichlet–Voronoi polyhedra were used to characterize the adjacent neighborhood of the ions in computer simulated configuration set of molten RbCl and LiI as examples of binary Coulomb liquids with like and unlike size ions, respectively. The statistical distribution of various features of the DV polyhedra has been studied with the following main results: (i) radial and angular distributions of adjacent neighbors indicate traces of face-centered-cubic symmetry in molten RbCl and wurtzite-like structure in LiI; (ii) the radial internal point distribution function on the DV polyhedra reveal more compact coordination spheres for Cl−, Rb+, and I− ions than for Li+ ions in the corresponding melts; (iii) the volume fluctuation of the DV polyhedra makes it possible to calculate isothermal compressibility coefficients even from (N,V,T) simulation data; (iv) identification of vacancies by seeking for the most protruding vertices of the DV polyhedra provides information on vacancy–vacancy pair correlation functions.