Na2Ge2Se5电子结构和光学性质的第一性原理研究

摘要

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 proper-ties 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.%Na2Ge2Se5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Na2Ge2Se5进行结构优化,并以此为基础计算研究了Na2Ge2Se5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4s,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Na2 Ge2 Se5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, Na2Ge2Se5是一种性能优良的红外非线性光学晶体材料.