Analysis of thermodynamic properties of molybdenum and tungsten at high temperatures

Using recent and accurate experimental information on various thermodynamic quantities up to the melting temperature Tf of molybdenum and tungsten, we make a detailed study of some of their high-temperature properties. In particular, we consider the entropy, reduced to a fixed crystal volume, and interpret the result in terms of an electronic part and a temperature-dependent entropy Debye temperature. The analysis reveals large explicit anharmonic effects. When plotted versus the reduced temperature T/Tf, various quantities of Mo and W related to anharmonicity show a striking similarity. For instance, the heat capacity CP is the same for Mo and W, to better than 1%, for T/Tf>0.2. We also make a detailed study of the temperature dependence of the Gr\"uneisen parameter at constant pressure and at constant volume.