Dynamic Structure Factor of Charge Density in Molten LiI by MD Simulation

Abstract

Dynamic structure factor of charge density was evaluated by MD simulation for molten LiI with artificially varied ionic masses. The dispersion curve was obtained from the peak frequency of collective excitation. The peak frequency at zero wavevector and the modulus of group velocity were estimated from the dispersion curves, as a function of ionic mass. The peak frequency at zero wavevector shows that the optic mode can be thermally excited for all the molten alkali halides. This suggests the ideas that the charge-density modes may dominate the thermal transport in these systems, and that insensitivity of the thermal conductivity of molten alkali halides to details of interionic potentials can be attributed to the behavior. The obtained modulus of group velocity was roughly proportional to m G −1/2 , where m G is the geometric average of anion and cation masses. This suggests that it may partially replace the mass term in the expression of thermal conductivity.