Dynamical sound speed and structural inhomogeneity in liquid Te studied by inelastic x-ray scattering

Inelastic x-ray scattering measurements using high-pressure apparatus were carried out for liquid Te up to 1673 K above the boiling point at the normal pressure. We could obtain the dynamic structure factor S(Q,E) of good quality at 1.8 ≤ Q ≤ 22 nm−1. Although the excitation energies of the acoustic mode are fluctuating more at lower temperatures, we found that the dynamical sound speed at 1.8 and 2.1 nm−1 becomes fast with increasing temperature from 773 to 923 K, similarly to the temperature dependence of ultrasonic sound speed in liquid Te. Despite this unusual temperature dependence at the lowest Q, the sound speed at higher Q is consistent with those obtained by the previous inelastic neutron and x-ray scattering studies, in which the dynamical sound just slows down with increasing temperature. The present results may be correlated with the temperature-driven semiconductor-metal transition in liquid Te, and if so, it is inferred that a domain size of inhomogeneity induced with the transition is comparable to the wave length corresponding to the lowest Q.