Structural, mechanical and thermodynamic properties of ZrO2 polymorphs by first-principles calculation

The structural, mechanical and thermodynamic properties of ZrO2 polymorphs (namely, monoclinic (P2(1)/c), tetragonal (P4(2)/nmc), cubic (Fm (3) over barm), and orthorhombic (Pbca and Pnma)) are investigated systematically by employing DFT functionals (LDA, PBE and PW91). It is found that the structural parameters of ZrO2 polymorphs calculated by PBE and PW91 functionals are highly consistent with previous experiments with low absolute relative error (ARE). Moreover, all considered structures are mechanically stable according to the Born-Huang criterion and the PBE and PW91 functionals are more accurate than the LDA functional in predicting mechanical and thermodynamic properties. Significantly, we described mechanical and thermodynamic properties of ZrO2 polymorphs by introducing the charge density difference of related surfaces, which provides a better understanding of different behaviors of elastic constants (C-ij) in various crystal structures of ZrO2.