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- 2018
高压下γ-Ca3N2晶体的结构，电子和光学性质的第一性原理研究
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Abstract:
采用广义梯度近似(GGA)框架下平面波超软赝势第一性原理方法，研究了γ-Ca3N2晶体在0~115 GPa高压下的结构、电子和光学性质.晶体中两种不同类型的Ca—N键长随压强的变化表明八面体的Ca—N键长比十二面体的键长有轻微的压缩.随着压强增大，价带向高能区移动，而导带向低能扩展，晶体的带隙变窄.基于Mulliken布局分析，γ-Ca3N2晶体随着压强增大，共价性增强.同时，在高压下晶体的吸收光谱显示出红移的趋势.
A plane wave ultrasoft pseudopotential implementation of first principles in the framework of the generalized gradient approximation (GGA) is utilized to calculate the structural, electronic and optical properties of the γ-Ca3N2 crystal under a hydrostatic pressure of 0-115 GPa. The change of bond lengths of two different types of Ca—N bond with pressure demonstrates that the octahedral Ca—N bond is slightly compressible compared to the dodecahedral Ca—N. As the pressure increases, the valence band moves toward the high energy region, while the conduction band extends toward the low energy region, and the band gap of the crystal becomes narrower. Based on the Mulliken population analysis, the crystal displays a much higher covalent character with increasing pressure. In addition, the absorption spectra of γ-Ca3N2 crystal show a trend of red shift under high pressure
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