Anisotropic electronic structure and geometry of CaMnO 3 perovskite with oxygen nonstoichiometry

摘要

The effects of oxygen nonstoichiometry on material formation, geometrical structure, and electronic structures together with carrier conductions of CaMnO3perovskite are comprehensively studied in detail. Specifically, the formation energy of oxygen nonstoichiometry in CaMnO3perovskite is 8.01eV. It has formation enthalpy of ?7.10eV. The MnO6octahedron is diminished alongbandc, it is expanded alonga. All Mn–O bindings tend to tilt and the MnO6octahedron is distorted. The strength of Mn–O bindings parallel to thea–cplane is enhanced; the strength of Mn–O bindings parallel to thebdirection is weakened. The band gaps are 0.804eV and 0.065eV for the CaMnO3and CaMnO2.75, respectively. The work functions are 4.69eV and 2.58eV, respectively. The p orbital electrons form the upper valance bands and the d orbital electrons form the lower conduction bands. The Ca s, Mn d and O p electrons contribute to carrier conductions for CaMnO2.75perovskite.