Ionic Dynamics of Alkali Chloride Systems in the Supercooled and Glassy States: Analyses of Inherent Structures

Abstract

Abstract Molecular dynamics simulations have been performed for two alkali chlorides, LiCl and LiCl-KCl, to investigate the relation between the finite-temperature real properties and the corresponding configurations of potential minima (Stillinger's inherent structures). The thermodynamic properties and the single-particle dynamical properties relevant to not vibrational but diffusive motions have been analyzed on the basis of quenched inherent structures. Each system include so large enthalpy gap and so large enthalpy fluctuation in their quenched configurations at around the glass transition temperature that both systems are found to be fragile liquids in Angell's scheme. It is found that the mean square displacements in the successive inherent structures exhibit Brownian behavior or linear time-dependence from very early time t = 0.01 ps, so that interbasin transitions represent the ionic diffusive behavior. The interbasin transitions can successfully describe Chemla's effect and an inverse phenomenon observed in real MD trajectory of the low-temperature liquids and glasses. Furthermore, we have revealed that there are three types of short-time intermittent interbasin transitions, namely, the jump-type transitions, non-jump-type residual motions, and residence in basins, all of which are hidden under vibrational motions at finite temperatures. As for the chemical difference, there are more prominent residual motions which are distinguished from the jump-type transitions in the LiCl-KCl glass than in the LiCl glass.