First-principles study of structural, mechanical, and thermodynamic properties of cubic Y2O3 under high pressure

The structural, mechanical, and thermodynamic properties of cubic Y2O3 crystals at different hydrostatic pressures and temperatures are systematically investigated based on density functional theory within the generalized gradient approximation. The calculated ground state properties, such as equilibrium lattice parameter a0, the bulk modulus B0, and its pressure derivative B0′ are in favorable agreement with the experimental and available theoretical values. The pressure dependence of a/a0 and V/V0 are also investigated. Furthermore, the elastic constants Cij, bulk modulus B, shear modulus G, Young's modulus E, the ductile or brittle (B/G), Vickers hardness Hv, isotropic wave velocities and sound velocities are calculated in detail in a pressure range from 0 to 14 GPa. It was found that the Debye temperature decreases monotonically with an increase in pressure, the calculated elastic anisotropic factors indicate that Y2O3 has low anisotropy at zero pressure, and that its elastic anisotropy increases as the pressure increases. Finally, the thermodynamic properties of Y2O3, such as the dependence of the heat capacities CV and CP, the thermal expansion coefficient α, the isothermal bulk modulus, and the Grüneisen parameter γ on temperature and pressure, are discussed from 0 to 2000 K and from 0 to 14 GPa, respectively, applying the non-empirical Debye model in the quasi-harmonic approximation.