Abstract

We have studied structural, electronic, optical, and elastic properties of KLiX under pressure using the Density Functional Theory (DFT) within the Generalized Gradient Approximation (GGA) and the Local Density Approximation (LDA) for the exchange and correlation potential. The obtained structural results such as lattice parameters and internal sites of K atoms and chalcogenides are in good accordance with the available experimental and theoretical data. Band structure analysis shows that these compounds exhibit semiconductor properties with an indirect gap (Z → Г) for KLiS, KLiSe and direct gap (Г → Г) in the case of KLiTe using GGA, but in the use of LDA all compounds have an indirect energy gap (Z → Г) which take values 3.258 (3.455), 2.723 (2.810), and 2.441 (2.685) eV for KLiS, KLiSe, and KLiTe using GGA (LDA) respectively. These energy gap values decreased with increasing chalcogenide size (S → Se → Te). The combination of the states density and the charge density analysis confirms mixing of an ionic and a covalent chemical bonding character in the studied compounds. The optical properties such as the dielectric function, absorption coefficient, optical reflectivity, refractive index, extinction coefficient, and electron energy loss are calculated for radiation up to 12 eV. The elastic constants and their pressure dependence are calculated using the static finite strain technique.

中文翻译：

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静水压力下KLiX（X：S，Se和Te）的结构，电子，光学和弹性性质的理论研究：伪势平面波（PP-PW）贡献

摘要

我们使用广义梯度逼近（GGA）和局部密度逼近（LDA）中的密度泛函理论（DFT）研究了KLi X在压力下的结构，电子，光学和弹性性质，以用于交换和相关势。获得的结构结果，例如晶格参数，K原子和硫族化物的内部位点，与现有的实验和理论数据吻合良好。能带结构分析表明，这些化合物表现出的半导体特性具有KLiS，KLiSe的间接间隙（Z →Г）和在使用GGA的KLiTe情况下的直接间隙（Г→Г），但是在LDA的使用中，所有化合物都具有间接能隙（Z→Г），分别使用GGA（LDA）对KLiS，KLiSe和KLiTe取值3.258（3.455），2.723（2.810）和2.441（2.685）eV。这些能隙值随着硫族化物尺寸的增加而减小（S→Se→Te）。状态密度和电荷密度分析的结合证实了所研究化合物中离子和共价化学键合特性的混合。计算出高达12 eV的辐射的光学特性，例如介电函数，吸收系数，光学反射率，折射率，消光系数和电子能量损耗。弹性常数及其压力相关性是使用静态有限应变技术计算的。