Intermediate range chemical ordering of cations in simple molten alkali halides

TL;DR

This study uses computer simulations to reveal intermediate range chemical ordering of Li+ ions in molten alkali halides, showing clustering and incomplete mixing despite simple interionic interactions.

Contribution

It demonstrates the presence of intermediate range ordering specifically for Li+ ions in molten alkali halides, a novel finding in simple ionic liquids.

Findings

Li+ ions form clusters in molten mixtures

Intermediate range ordering appears only for Li+

Clustering indicates incomplete local mixing

Abstract

The presence of first sharp diffraction peaks in the partial structure factors is investigated in computer simulations of molten mixtures of alkali halides. An intermediate range ordering appears for the Li+ ions only, which is associated with clustering of this species and is not reflected in the arrangement of other ions. This ordering is surprising in view of the simplicity of the interionic interactions in alkali halides. The clustering reflects an incomplete mixing of the various species on a local length scale, which can be demonstrated by studying the complementary sub-space of cations in the corresponding pure alkali halides by means of a void analysis.