LiBX2 (B=Ga, In; X= S, Se, Te)光学性质与力学性质的第一性原理计算

采用基于第一性原理的赝势平面波方法系统地计算了LiBX₂ (B= Ga, In; X= S,Se,Te) 晶体的光学性质与力学性质. 由禁带宽度推断出晶体抗激光损伤阈值的大小顺序为LiGaS₂ > LiInS₂ > LiGaSe₂ > LiInSe₂ > LiGaTe₂ > LiInTe₂. 六种晶体在常压下均满足机械力学稳定性要求, 且铟化合物可塑性及延展性强于镓化合物. 这些晶体的静态电介电常数 ε₁(0)、静态折射率n(0)和双折射率Δn 理论计算值与实验值相符. LiGaS₂, LiInS₂, LiGaSe₂, LiInSe₂和LiGaTe₂五种化合物双折射率较高, 并且它们的吸收谱与反射谱在中远红外区是透过的, 因此可推断出这五种化合物可以成为优异的中远红外非线性光学材料.

First-principles calculations of optical and mechanical properties of LiBX2 (B= Ga, In; X= S, Se, Te)

First-principles calculations of optical and mechanical properties of LiBX₂ (B= Ga,In; X= S,Se,Te) are performed using plane-wave pseudopotential method. According to the order of band gaps, the order of laser induced damage thresholds is LiGaS₂ > LiInS₂ > LiGaSe₂ > LiInSe₂ > LiGaTe₂ > LiInTe₂. The elastic constants of these crystals can all meet the mechanical stability conditions at normal pressure, and the plasticitics and ductilities of indium compounds are better than those of gallium compounds. Theoretical values of average static electronic dielectric constant ε₁(0), average ordinary refraction index n₀ and birefringence index Δn of these crystals are in good agreement with the experimental data. LiGaS₂, LiInS₂, LiGaSe₂, LiInSe₂ and LiGaTe₂ compounds have the large birefringences and their absorption and reflectivity spectra are transmissible through mid- and far-IR region, so the five crystals are likely to be promising materials for nonlinear optical applications in the mid- and far-IR region.