立方KCaF_3电子、弹性和光学性质的第一性原理研究

基于密度泛函理论和赝势平面波近似法计算研究了立方钙钛矿KCaF_3的弹性、电子和光学性质.基态时,KCaF_3平衡晶格常数、体积弹性模量和实验及其他计算值一致.根据Hooke定律和Christoffel方程,研究了KCaF_3弹性常数Cij、体积弹性模量B、各向同性波速和弹性各向性异性因子随压力的变化关系.从电子能带理论出发,计算得到了KCaF_3电子能带、态密度和Milliken电荷布居数,并对其电子性质进行了详细分析.结果显示:立方钙钛矿KCaF_3为直接带隙绝缘体材料,其禁带宽度为6.22 e V;电荷主要从Ca和K原子向F原子转移;立方钙钛矿KCaF_3属于纯粹的共价型化合物.同时,本文还计算研究了KCaF_3的光学介电函数、吸收系数、复折射率、能量损失谱和反射系数等光学性质.

First principles study of electronic, elastic and optical properties of cubic KCaF3

The electronic, elastic and optical properties of cubic perovskite KCaF3 were investigated using the pseudo-potential plane wave method within the density functional theory. At ground state, the calculated equilibrium lattice a and bulk modulus B0 are in a reasonable agreement with the experimental and other theoretical data. According to the Hooke''s law and equation of Christoffel, the dependences of the elastic constants Cij, bulk modulus B, isotropic wave velocities and elastic anisotropic factors with the pressure were investigated. From the theory of electronic band structure, we have calculated the band structure, density of states and Mulliken population for cubic perovskite KCaF3 in detail. The results indicate that the cubic perovskite KCaF3 is a direct band gap insulator material, the value of the band gap is 6.22 eV, the charge transfer is main from Ca and K atom to F atom. KCaF3 is pure covalent bond chemical compounds. At the same time, the dielectric function, adsorption coefficient, refractive index, loss function and reflection coefficient of KCaF3 were calculated and investigated in this work.