The detailed crystal and electronic structures of the cotunnite-type ZrO2

Abstract

Abstract The detailed crystal and orbital-decomposed electronic structures of cotunnite-type ZrO2 have been investigated by using the first-principles projector augmented wave (PAW) potential within the generalized gradient approximation as well as taking into account on-site Coulomb repulsive interaction (GGA+U). The optimized structure shows that the O I and O II anions are surrounded by an arbitrary tetrahedron of four Zr cations and an arbitrary pentahedron of five Zr cations, respectively, in turn, the Zr cation is surrounded by an arbitrary tetrakaidecahedron formed by nine oxygen ligands. Although one more Zr cation is coordinated to O II , the larger bond lengths between O II and its adjacent five Zr cations ( d O II − Zr ) than those between O I and its adjacent four Zr cations ( d O I − Zr ) makes density of states (DOS) of s and three p ( p x , p y and p z ) states of the O II anion driving down in lower energy region and driving up in higher energy region. No crystal-field splitting is observed between three p ( p x , p y and p z ) states of anions O I and O II (between three p ( p x , p y and p z ) states and five d ( d xy , d yz , d xz , d z 2 and d x 2 - y 2 ) states of cation Zr) is resulted from the arrangements of the surrounding cations (anions) do not have any symmetry. The additional covalent character upon Zr–O ionic bonds is attributed to the hybridization of itinerant Zr(5s) and less filled Zr(4d) states to the separated O(2s) and O(2p) states.