Electrical Conductivity of Molten Salts and Ionic Conduction in Electrolyte Solutions

Abstract

A microscopic description for the partial DC conductivities in molten salts has been discussed by using a Langevin equation for the constituent ions. The memory function γ(t) can be written as in the form of a decaying function with time. In order to solve the mutual relation between the combined-velocity correlation functions Z σ AE (t) and the memory function γ(t) in a short time region, a new recursion method is proposed. Practical application is carried out for molten NaCl by using MD simulation. The fitted function is described by three kinds of Gaussian functions and their physical backgrounds are discussed. Also the electrical conductivity in aqueous solution of electrolyte has been obtained, based on a generalized Langevin equation for cation and anion in it. This treatment can connect and compare with the work of computer simulation. The obtained results for concentration dependence of electrical conductivity are given by a function of the square root of concentration. The electrophoretic effect and the relaxation one are also discussed.

Microscopic origins of conductivity in molten salts unraveled by computer simulations

“…Based on the partial conductivities, they claim that the Al 3+ ion travels on average in overall negatively charged clusters, AlF n 3−n with n > 3, towards the positively charged electrode. However, we noticed that the partial conductivity values determined by Gheribi et al 15 are not compatible with the universal golden rule 36,37 , even for the simplest case, i.e., pure NaF, which is also an alkali halide such as the pure LiF, LiCl, and LiI, investigated here without any need for assumptions. Indeed, Koishi et al 23 showed that the universal golden rule holds for molten NaCl as well.…”

“…This demonstrates that the effective electrical mobility values b EF take cross-correlation effects into account correctly. For the pure molten salts (see Supplementary Note 4 and Supplementary Table 3), Sundheim's universal golden rule, σ + /σ − = m − /m +36,37 , obtained from the generalized Drude theory as a law of motion under an electric field 22,23,37 , is found to hold true. The rule can be extended to binary and ternary mixtures 38 ; in our case,…”