Ab initio study of generalized collective excitations in molten NaI

A combination of ab initio molecular dynamics and parameter-free analysis of time-correlation functions based on the generalized collective mode approach is applied for the study of collective dynamics in a molten salt NaI beyond the hydrodynamic region and manifestation of collective excitations in dynamic structure factors. The dispersion and damping of acoustic and optic modes as well as the wave-number dependence of relaxation processes are discussed. Contributions from opticlike modes to the total and concentration dynamic structure factors are estimated. Analysis of the inelastic x-ray scattering (IXS)-weighted total dynamic structure factor at T=953 K is performed in order to verify the possibility of direct observation of optic modes in molten NaI in the IXS experiments.