E. I. Andritsos, E. Zarkadoula, A. E. Phillips, M. T. Dove, C. J. Walker, V. V. Brazhkin, K. Trachenko
We propose a new simple way to evaluate the effect of anharmonicity on a system's thermodynamic functions such as heat capacity. In this approach, the contribution of all potentially complicated anharmonic effects to constant-volume heat capacity is evaluated by one parameter only, the coefficient of thermal expansion. Importantly, this approach is applicable not only to crystals but also to glasses and viscous liquids. To support this proposal, we perform molecular dynamics simulations of several crystalline and amorphous solids as well as liquids, and find a good agreement between results from theory and simulations. We observe an interesting non-monotonic behavior of liquid heat capacity with a maximum, and explain this effect as a result of competition between anharmonicity at low temperature and decreasing number of transverse modes at high temperature.
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http://arxiv.org/abs/1302.3477
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