Anion Polarization Effects on Static Structure and Ionic Transport in Superionic Melt of RbAg4I5

Abstract

The anion polarization effects on the static structure and ionic transport in the superionic melt of RbAg4I5 are investigated by molecular dynamics simulations with the rigid ion model and the polarizable ion model (PIM). The first sharp diffraction peak (FSDP) observed in the experimental static structure factor is reproduced in the case of the PIM, and cation–cation partial structure factors show the characteristic FSDP for Ag–Ag and Rb–Rb correlations and a negative FSDP for the Ag–Rb correlation, indicating that Ag and Rb ions are alternately distributed with an intermediate-range length scale. Ag ions form small clusters of the various sizes, which relates to the density fluctuation and intermediate-range ordering of Ag ions. Rb and the surrounding I ions generate the regions where Ag ions cannot penetrate with the radius of 4–5 A, which is revealed by void analysis by the Voronoi–Delaunay method. The superionic feature remains even in the molten state since the diffusion coefficient of Ag ions is se...