Unified Landau description of tetragonal-orthorhombic-monoclinic zirconia

We compute an explicit lowest-order polynomial form of the strain-dependent Gibbs potential which provides a unified description of the tetragonal, orthorhombic, and monoclinic phases of zirconia (ZrO2). The resulting energy function interpolates well the available experimental data for this material, reproducing its known elastic moduli, equilibrium strains, and phase diagram to about 1700 K and 8 GPa