Ba置换对钙钛矿型氧化物CaMnO3稳定性及电子结构的影响
Effects of Ba Substitution on Stability and Electronic Structure of Perovskite CaMnO3 Oxide

采用赝势法近似密度泛函理论的方法研究了重元素Ba置换钙钛矿型氧化物CaMnO3的稳定性及电子结构。结果表明，Ba置换引入晶格畸变，且具有各向异性。Ba置换钙钛矿型氧化物CaMnO3呈现明显的半导体特性，且其稳定性降低。Ba置换Ca位之后，钙钛矿型氧化物CaMnO3仍然呈间接带隙型能带结构，自旋向上和自旋向下的电子能带带隙宽度分别减小到0.659eV和0.655eV，且经过Ba置换之后向导体转变。Ba置换CaMnO3晶体中的电子主要在-37.5eV，-18 eV，-16 eV，-5eV～0eV，1eV附近形成能带，能级数量在-18 eV，-16 eV，-0.7 eV三个极值点依次降低。Ba置换钙钛矿型氧化物CaMnO3价带中和导带中的电子能级弥散性不同，表明它们具有不同的有效质量。Mnp，Op和Mnd电子对钙钛矿型氧化物CaMnO3费米面态密度具有较大的贡献，它们决定CaMnO3材料的导电过程。
The stability and electronic structure of the heavy element Ba substituted perovskite type oxide CaMnO3 have been studied by the psudo-potential approximation density funtional theory calculation method. The results show that the lattice distortion has been induced by Ba substitution and the distortion is anisotropic. The Ba substituted perovskite type oxide CaMnO3 exhitbites semiconductor character and the stability decreases. The indirect band gap has been remained by Ba substitution for Ca site for the perovskite type oxide CaMnO3 yet, the band gaps of the spin up electrons and the spin down electrons have been slightly decreased to 0.659eV and 0.655eV, respectively. The semiconductor to conductor transition has also been found. The electrons of the Ba substituted perovskite type oxide CaMnO3 form energy bands near -37.5eV，-18 eV，-16 eV，-5eV～0eV and 1eV, and the peak values of the density of states curve decreases along with the energy regions of -18 eV，-16 eV and -0.7 eV. The dispersion characters of the bands within the valance bands and the conduction bands are much different, which indicate their diverse effective mass. The Mnp, Op and the Mnd electrons have contributtion to the density of states at the Fermi level, these electrons determine the conduction process of the titled oxide materials.