立方KCaF_3电子、弹性和光学性质的第一性原理研究

First principles study of electronic,elastic and optical properties of cubic KCaF_3

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.

The electronic , elastic and optical properties of cubic perovskite KCaF 3 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 reasonable agreement with the experimental and other theoretical data .According to the Hooke＆#39;s law and equation of Christoffel , the de-pendences 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 KCaF 3 in detail.The results indicate that the cubic perovskite KCaF 3 is a direct band gap insulator material , the value of the band gap is 6.22 eV, the charge transfer is mainly 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 coeffi-cient of KCaF 3 were calculated and investigated in this work .