STRUCTURAL-PROPERTIES AND QUASI-PARTICLE BAND-STRUCTURE OF ZIRCONIA

We report ab initio calculations of the structural and quasiparticle p roperties of ZrO2, otherwise known as zirconia. The plane-wave pseudop otential method is used to compute the structural properties of the cu bic, tetragonal, and monoclinic phases of zirconia. Oxygen vacancies i n the cubic phase are also studied using a supercell approach. The str uctural parameters, including all internal degrees of freedom of all p hases, are relaxed. Excellent agreement is achieved with experiment an d with other ab initio calculations available. We compute the quasipar ticle band gaps within Hedin's GW approximation using the method of Hy bertsen and Louie, and confirm that the quasiparticle approach can be successfully applied to transition-metal oxides if the core-valence ov erlap is small. We predict the fundamental gap of pure cubic, tetragon al, and monoclinic zirconia to be 5.55 eV, 6.40 eV, and 5.42 eV, respe ctively. Within the GW approximation, the oxygen vacancy state in the cubic phase is found to be nondegenerate, fully occupied, and well sep arated from the valence and conduction bands, positioned 2.1 eV below the conduction band edge.