Theoretical investigations on the structural, elastic and thermodynamic properties of dysprosium hafnate

The lattice structure and elastic properties of Dy2Hf2O7 at 0 K and 0–40 GPa are calculated by using first-principles methods. The results show that the calculated structural parameters are in good agreement with the experimental values. The elastic constants increase with the increase of pressure, and all the elastic constants satisfy the Born criterion, that is, the Dy2Hf2O7 crystal is kinetically stable within the range of the calculated conditions. In addition, the thermodynamic properties of Dy2Hf2O7 crystal at different temperatures (0–2000 K) and pressures (0–40 GPa) are calculated by using the quasi-harmonic Debye model, and the temperature-pressure dependence of thermodynamic properties, such as the heat capacity, coefficient of thermal expansion, and Debye temperatures, is obtained and compared with the experimental values. We also obtain the melting point and hardness of Dy2Hf2O7 compound by using empirical formulas in the literature.