PHASE TRANSITIONS AND ELASTICITY IN ZIRCONIA.
The potential induced breathing (PIB) model is used to calculate equations of state, relative phase stabilities, and elasticity of several different structures of ZrO//2. PIB is a non-empirical model for calculation of static and dynamic properties of ionic crystals. The cubic fluorite structure is found to be the stable zero-pressure phase. The monoclinic phase is more stable at low densities and the PbCl//2 phase is more stable at high pressures. The rutile structure is found to be relatively unstable, a result in agreement with experiment. Elastic constants are calculated for the monoclinic, tetragonal, and fluorite phases of ZrO//2. For the pure monoclinic phase, good agreement with experiment is found for the aggregate shear and Young's moduli. The elastic constants and pressure derivatives for cubic zirconia are discrepant with experimental data, and it is suggested that disorder greatly affects its elastic behavior. Furthermore, disorder and defects may be important in stabilizing the monoclinic and tetragonal structures.