Transverse acoustic phonon excitations in liquid metals

Abstract

Abstract In this article, transverse acoustic (TA) phonon excitations in various liquid metals are reviewed. Low-frequency TA phonon excitations were investigated on liquid Ga, Sn, Fe, Cu, Zn, and Bi, by using high energy resolution inelastic X-ray scattering (IXS). The current correlation functions obtained from the IXS spectra were analyzed by using two Gaussians to evaluate the excitation energies and widths of the longitudinal acoustic and TA excitation modes, which are consistent with ab initio molecular dynamics simulations. The lifetimes and propagating lengths of the TA modes were determined, and may respectively correspond to the lifetimes and sizes of cages instantaneously formed in each liquid metal. The microscopic elastic constants were estimated and characteristic differences from macroscopic polycrystalline values were found in Poisson’s ratios. Future experimental and analytical problems to be solved in the near future are addressed.