Structure and self-diffusion at temperatures close to the melting point were studied using first-principles Hellmann-Feynman molecular dynamics. The results were compared with classical molecular dynamics using rigid-ion and shell-model inter-ionic potentials. The main differences between the structures predicted by Hellmann-Feynman molecular dynamics and rigid-ion molecular dynamics for NaI concerned the cation-cation and anion-cation pair correlation functions. A shell model which allowed only for the polarization of I- reproduced the main features of the Hellmann-Feynman molecular dynamics structure of NaI. The inclusion of polarization effects for both ionic species led to a more structured ionic liquid, although good agreement with Hellmann-Feynman molecular dynamics was also observed. The Hellmann-Feynman molecular dynamics Green-Kubo self-diffusion coefficients were larger than those obtained from rigid-ion and shell-model simulations. Hirshfeld charge distributions indicated that differences between the results were related mainly to polarization effects, while the influence of charge transfer fluctuations was minimal.

First Principles Molecular Dynamics of Molten NaI: Structure, Self-Diffusion, Polarization Effects, and Charge Transfer. Galamba, N., Costa Cabral, B.J.: Journal of Chemical Physics, 2007, 127[9], 094506