高压下LiF和NaF的结构稳定性及其电子和光学性质的第一性原理研究

基于密度泛函理论，采用全势线性缀加平面波加局域轨道方法，计算模拟了LiF高压下的相变行为，预测其在450GPa附近发生由NaCl结构(B1)到CsCl结构(B2)的结构相变.同时还计算了高压下LiF不同相的电学特性，LiF的复介电函数以及介电常数随压强变化关系.通过比较能带结构的变化行为，得出LiF在53GPa附近还存在等结构相变，即由直接带隙结构变为间接带隙结构.将LiF的计算结果与另外一个同构化合物NaF进行了比较讨论. 关键词： LiF 压致相变 从头计算

First principles investigation of structural stability and electronic and optical properties of LiF and NaF under high pressure

First principles calculation of LiF and NaF (NaCl phase and CsCl phase) underhigh pressure was carried out with the full potential linearized augmented plane wave plus local orbital method. It was shown that NaCl-type LiF transforms to a CsCl-type phase at about 450 GPa. Calculations of the electronic properties of LiF at high pressure compared with the energy band structural information indicate that a non-structureal transition occurs at about 53GPa, in which the direct band structure transforms to an in-direct band structure. We also calculated the complex electronic dielectric function and the static dielectric constants of LiF as functions of pressure. The results obtained for LiF are also compared with siilar data of NaF system.