Transverse excitations in liquid Fe, Cu and Zn

Transverse acoustic (TA) excitation modes were observed in inelastic x-ray scattering spectra of liquid Fe, Cu and Zn. From the analysis of current correlation functions, we concluded that TA excitation modes can experimentally be detected through the quasi-TA branches in the longitudinal current correlation spectra in these liquid metals. The microscopic elastic constants are estimated and a characteristic difference from macroscopic polycrystalline value was found in Poisson's ratio of liquid Fe, which shows an extremely softer value of similar to 0.38 compared with the macroscopic value of similar to 0.275. The lifetime of the TA modes were determined to be similar to 0.45 ps for liquid Fe and Cu and similar to 0.55 ps for liquid Zn, reflecting different interatomic correlations between liquid transition metals and non-transition metals. The propagation length of the TA modes are similar to 0.85 nm in all of liquid metals, corresponding to the size of icosahedral or similar size of cages formed instantaneously in these liquid metals.