Dispersion relations of the acoustic modes in divalent liquid metals

Collective dynamics in liquid Ca and liquid Cd was studied by inelastic x-ray scattering (IXS). Using our experimental technique to prepare proper sample cells and high performance of an IXS beamline (BL35XU) at SPring-8 in Japan, the dynamic structure factor with reasonable statistics was obtained for these divalent liquid metals. For both liquids, the dynamic structure factor at low Q exhibits a central peak with a shoulder or small hump clearly visible on each side, and the inelastic excitation energy determined using the model function composed of Lorentzian and the damped harmonic oscillator function disperses with increasing Q . The dispersion curves of these liquids were compared with that of the longitudinal acoustic phonon in each crystalline phase. From these results, clear difference in the interatomic interaction be- tween liquid Ca and liquid Cd was inferred.