Na掺杂CaMnO3晶体材料的结构调控、电子结构与光吸收性质的研究

Geometry Modulation,Electronic Structure and Absorption Properties of Na Doped CaMnO3 Crystalline Material

平面波和赝势法基础上研究了Ca位Na掺杂的钙钛矿型CaMnO3晶体材料的晶体结构、电子结构和光吸收性质,分析了Na掺杂CaMnO3晶体材料的电输运过程。结果表明,Na掺杂Ca位使CaMnO3的晶胞三轴长度均增大,Na掺杂在CaMnO3中引入了晶格畸变,且晶格畸变是各向异性的。Na掺杂之后,CaMnO3晶体材料内的O-Mn-O形成的八面体逐步向两个O顶点方向拉长和扭曲。未掺杂和Na掺杂CaMnO3带隙宽度分别为0.713eV和0.686eV,均呈现明显的半导体特性。在费米能级附近,s态电子对CaMnO3的态密度贡献最小,p态电子对费米能级以下的态密度贡献最大,d态电子对费米能级以上的态密度贡献最大。Mnp态电子对费米能下方能级形成贡献较大,而Mnd态电子对费米能上方能级形成贡献最大,Op态电子对费米能下方能级形成贡献较大,而Op态电子对费米能上方能级形成贡献最小。与未掺杂CaMnO3相比,Na掺杂CaMnO3晶体材料吸收能量向低能量移动,且存在两个强吸收峰,其在6.15eV附近的吸收最强。

The geometric structure, electronic structure and the optical absorption properties of the Na doped perovskite type CaMnO3 crystalline material for Ca site have been studied by the plane wave as well as the pseodopotential method, and the electrical transport process has also been analyzed. The results show that the axis of the three dimentions increases, the lattice distortion has also been induced, and the lattice distortion is geometrically anisotropic. The O-Mn-O octahedron is lengthened along the two O pole direction, and the O-Mn-O octahedron is also twisted. The band gaps for the undoped and the Na doped CaMnO3 crystalline materials are 0. 713 eV and 0. 686 eV, respectively. The two types of materials are all semiconductors. Near the Fermi level, the s state electrons contribute to the density of state the least, and the p state electrons contribute to the density of state most under the Fermi level, the d state electrons contribute to the density of state most above the Fermi level. The Mnp state electrons contribute to the energy band formation most under Fermi level, and the Mnd state electrons contribute to the energy band formation most above the Fermi level. The Op state electrons contribute to the energy band formation moderately more under Fermi level, while the Op state electrons contribute to the energy band formation least above the Fermi level. Comparing to the un-doped CaMnO3 crystalline material, the optical absorption region moves to the low energy region, the Na doped CaMnO3 crystalline material has two absorption peaks, and the absorption peak at 6. 15 eV is the most strongest.