Thermal properties ofCaMoO4: Lattice dynamics and synchrotron powder diffraction studies

The structure of calcium molybdate was studied by means of synchrotron based high-resolution powder diffraction methods in the temperature range $12–300\mathrm{K}$. The scheelite structure type was confirmed for $\mathrm{Ca}\mathrm{Mo}{\mathrm{O}}_4$ in the temperature region investigated and no structural anomalies were observed. Thermal expansion coefficients extracted from the thermal dependencies of the cell sizes are found to be in good agreement with the predictions from our lattice dynamics calculations that form the background for microscopic interpretation of the experimental data. From the analyses of experimental results and the calculated thermal expansion coefficients, elastic constants, phonon density of states, heat capacities, entropy, and Grüneisen parameters it is concluded that a quasiharmonic lattice dynamics approach provides a good description of these properties for $\mathrm{Ca}\mathrm{Mo}{\mathrm{O}}_4$ at temperatures below $800\mathrm{K}$.