高压下MgMoO₄晶体结构与光学性质的第一性原理研究

Study on First-Principles of Crystal Structure and Optical Properties of MgMoO₄ under High Pressure

摘要: 本文基于第一性原理计算的方法，利用密度泛函理论中的广义梯度近似，分别对MgMoO₄晶体的两种结构(β-MgMoO₄和γ-MgMoO₄)进行了优化，得到能量最低的稳定构型，在此基础上计算了不同压力下的电子结构和光学性质。研究发现，MgMoO₄的带隙随压力的增加而减小，压致相变的同时，能带结构发生了从直接带隙到间接带隙的转变。相变后，γ-MgMoO₄的极化能力变强，有利于电子空穴对的分离，说明压力有助于改善材料的光催化活性。吸收光谱主要为紫外吸收，高能区吸收峰的强度随压力的增加而增大，有较高的吸收系数。压致相变后的反射峰强度明显增加，压力增大了MgMoO₄的反射率。根据本文电子结构和光学性能的计算，表明MgMoO₄在电子和光电子器件、紫外发光方面具有潜在的应用价值。

Abstract: In this paper, based on the first-principles calculation method, the generalized gradient approximation density functional theory was used to optimize the two kinds of geometrical structure of MgMoO₄ (β-MgMoO₄ and γ-MgMoO₄), and the lowest-energy stable configurations were obtained. On this basis, the electronic structure and optical properties of MgMoO4 under different pressures were calculated. The study found that the band gap of MgMoO₄ decreases with the increase of pressure, and the transition from direct band gap to indirect band gap occurs during the pressure-induced phase transition. After the phase transition, the polarization ability of γ-MgMoO₄ becomes stronger, which is conducive to the separation of electron-hole pairs, indicating that the pressure is conducive to the improvement of the photo-catalytic activity of the material. The absorption spectrum is mainly ultraviolet absorption, and the absorption peak intensity in the high-energy region increases with the increase of pressure with a high absorption coefficient. The intensity of reflection peak increased obviously after pressure transition, and the pressure increases the reflectivity. According to the examination of the electronic structure and optical properties in this paper, MgMoO4 has potential application value in electronic and optoelectronic devices and ultraviolet luminescence.