Shell model molecular dynamics calculations of the Raman spectra of molten NaI

The shell model used in lattice dynamics is applied to construct an interionic potential for use in molecular dynamics (MD) simulations of molten NaI. The ion shell-core displacements generated by the shell model potentials are used as an approximation to the instantaneous dipole moments of the ions. Time correlation functions of aggregates of these instantaneous ionic dipoles are related to the polarised and depolarised Raman spectra of the melt; fair agreement between simulated and experimentally observed spectra is obtained, indicating that the dipole-induced-dipole mechanism is an important component but not the exclusive contributor to the Raman polarisability in ionic melts.