The collective dynamics of the ‘non-simple’ liquid metal Sn

Abstract The dynamic structure factor S ( Q , ω ) of liquid Sn was measured at 320 °C and 1000 °C in a Q -range between 2 nm −1 and 30 nm −1 using inelastic X-ray scattering. The obtained spectra clearly demonstrate the existence of longitudinal propagating modes in this liquid metal. At 320 °C a positive dispersion is found in the low Q -region, where the mode velocity is about 12% larger than the bulk adiabatic speed of sound. At 1000° this so-called ‘positive dispersion’ reduces to about 6%. The quasielastic lineshape contains a Gaussian contribution near the Q -positions of the first maximum in S ( Q ), which has not yet been reported in simple liquid metals like, e.g. the liquid alkalis. With increasing temperature, the relative Gaussian contribution increases and can be observed along a wider Q -range. This anomaly is related to a partially covalent nature of liquid Sn in analogy to other liquid non-simple metals.