Sound velocity is a fundamental measure of the thermodynamic state of the liquid. It has long been suspected that deviations from normal behavior, i.e. linear decrease of the sound velocity with temperature, are indicative of structural rearrangements. Liquid antimony (l-Sb) exhibits an anomalous temperature dependence of the sound velocity with a maximum value attained at approximately 900⁰C [1]. We have measured the pair correlation function in l-Sb at relatively small temperature intervals across a wide temperature range and obtained the temperature dependence of the parameters of the structure. We find that the temperature dependence of the structure is correlated with that of the sound velocity [2]. We find that similar correlations exist in other liquid metals. A simple thermodynamic relation, which relates the temperature dependence of the sound velocity in the liquid with other thermodynamic quantities, was derived. It is seen that in normal liquids the temperature dependence is related to the volume expansion coefficient. In anomalous liquids the increase in temperature is seen to originate in an entropy term and may be associated with structural rearrangements. A microscopic model for anomalous liquid metals is proposed.

[1] Y. Greenberg, E. Yahel, M. Ganor, R. Hevroni, I. Korover, M. P. Dariel and G. Makov, J.   Non-Cryst. Sol. 354, 4094 (2008).

[2] Y. Greenberg, E. Yahel, El’ad N. Caspi, Brigitte Beuneu, M. P. Dariel and G. Makov, J. Chem Phys. 133, 094506 (2010).