文摘
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 OI and OII 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 OII, the larger bond lengths between OII and its adjacent five Zr cations (dOII−Zr) than those between OI and its adjacent four Zr cations (dOI−Zr) makes density of states (DOS) of s and three p (px, py and d059f1fd364fedb48dbe0ec8994" title="Click to view the MathML source">pz) states of the OII anion driving down in lower energy region and driving up in higher energy region. No crystal-field splitting is observed between three p (px, py and d059f1fd364fedb48dbe0ec8994" title="Click to view the MathML source">pz) states of anions OI and OII (between three p (px, py and d059f1fd364fedb48dbe0ec8994" title="Click to view the MathML source">pz) states and five d (dxy, 82d655cdfdc253b19fda2" title="Click to view the MathML source">dyz, dxz, dz2 and dx2-y2) 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.