KZnF3cubic perovskite. Heat capacity and lattice dynamics

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Abstract
The elastic constants of the cubic perovskite KZnF3 have been measured from 4 to 300 K. Heat capacity data, Cp, and elastic constants have been analysed and compared with the predictions from the lattice dynamics within a rigid-ion model. Phonon dispersion curves at different temperatures, heat capacity and Debye temperatures theta D(T), have been obtained for this model from the density of states of the lattice vibrational spectrum, taking into account the temperature dependence of the parameters. The values have been calculated both in the quasi-harmonic approximation and with anharmonic corrections. They have been compared with the heat capacity data; a good agreement is found. The small discrepancies have been explained by considering the limitations in the description of the lattice dynamics in the model used.