Na_2Ge_2Se_5电子结构和光学性质的第一性原理研究

Na_2Ge_2Se_5是一种优异的红外非线性晶体材料.采用基于第一性原理的密度泛函理论赝势平面波方法对Na_2Ge_2Se_5进行结构优化,并以此为基础计算研究了Na_2Ge_2Se_5的电子结构和光学性质.结果表明:Na2Ge2Se5是宽禁带间接带隙半导体,价带至导带的电子跃迁主要来自于Ge和Se的48,4p态;Na对光学性质的贡献较小,Ge和Se之间的相互耦合作用决定了Na_2Ge_2Se_5的光学性质;该晶体在紫外区有强烈的反射和吸收,静态折射率为2.133,双折射率值适中,为0.145.理论计算结果表明,Na_2Ge_2Se_5是一种性能优良的红外非线性光学晶体材料.

First principles study on the electronic structures and optical properties of Na2Ge2Se5

The optimized crystal structure, electronic structure and optical properties of Na₂Ge₂Se₅, an excellent nonlinear crystal, are investigated by using pseudo-potential plane-wave method based on the first principles. The band structure, density of states, bond population, dielectric function, reflection spectrum, absorption spectrum, and codex refractive index of optimized structure of Na₂Ge₂Se₅ are calculated. The results indicate that Na₂Ge₂Se₅ is indirect wide-band semiconductor. The electronic transitions are mainly composed of Ge-4s, Ge-4p, Se-4s and Se-4p. The optical properties are determined by the interaction between Ge and Se, while Na contributes little. The reflectance spectrum and absorption spectrum indicate that there is strong absorption to ultraviolet radiation and static refractive index is 2.133. Na₂Ge₂Se₅ possesses moderate birefringence. The results indicate that Na₂Ge₂Se₅ is a good candidate for the optical crystals in the infrared region.
Keywords： 2Ge₂Se₅')" href="#">Na₂Ge₂Se₅ electronic structure optical properties first-principles