Static structure and ionic transport in molten AgBr and AgCl

Abstract

The static structure of molten AgBr and AgCl have been calculated using the hypernetted chain theory of liquids ~HNC! and molecular dynamics simulations ~MD! with effective potentials based on the functional form originally proposed by Vashishta and Rahman @Phys. Rev. Lett. 40, 1337 ~1978!# to study a-AgI. The HNC and MD are in good agreement among themselves as well as in good qualitative agreement with experiment. MD simulations have been also used to calculate the time correlation functions and ionic transport properties of these melts. The results for the velocity autocorrelation functions suggest, in both cases, a mechanism for diffusion akin to that we suggested for molten AgI and CuX (X5Cl, Br, I) @J. Phys. Condens. Matter 2, 6643 ~1990!# even though the cations velocity autocorrelation function is no longer purely diffusive. The results for the diffusion coefficients resemble the type of behavior found in superionic melts, as if the transition to a superionic state is finally realized in AgCl and AgBr on melting. The results for the specific ionic conductivities are in good agreement with experiment if it is assumed that the ions, in their transport, carry with them their full complement of electrons.