Department of Physics, University at Buffalo, SUNY, Buffalo, NY 14260, USA.
J Phys Condens Matter. 2012 Feb 29;24(8):085602. doi: 10.1088/0953-8984/24/8/085602. Epub 2012 Jan 26.
The quasiparticle and optical properties of magnesium fluoride (MgF(2)) are computed within the GW approximation based on many-body perturbation theory (MBPT). The many-body effects appearing in self-energy and electron-hole interactions have an important influence on the electronic and optical properties. The DFT-LDA calculation shows a 6.78 eV band gap. Two methods are employed to evaluate the self-energy within the GW approximation in the present work. The generalized plasmon pole model (GPP) provides a band gap of 12.17 eV, which agrees well with the experimental value of 12.4 eV (Thomas et al 1973 Phys. Status Solidi b 56 163). Another band gap value of 11.30 eV is obtained by using a full frequency-dependent self-energy, which is also not far from the experimental value and is much better than the result from the LDA calculation. The calculated optical spectrum within DFT is significantly different from the experiment. Although the calculated optical absorption threshold within the GW method is close to the experiment, the overall shape of the spectrum is still similar to the case of DFT. However, the overall shape of the spectrum via the Bethe-Salpeter equation (BSE) method agrees well with the experiment.
在基于多体微扰理论（MBPT）的 GW 近似下，计算了氟化镁（MgF2）的准粒子和光学性质。自能和电子-空穴相互作用中出现的多体效应对电子和光学性质有重要影响。DFT-LDA 计算得到的带隙为 6.78eV。本文采用两种方法在 GW 近似下评估自能。广义等离子体极点模型（GPP）给出的带隙为 12.17eV，与实验值 12.4eV（Thomas 等人，1973 年，物理状态 Solidi b 56 163）吻合较好。另一个带隙值 11.30eV 是通过使用全频相关自能得到的，它也与实验值相差不远，且优于 LDA 计算的结果。DFT 计算的光学谱与实验显著不同。虽然 GW 方法计算的光吸收阈值与实验接近，但谱的整体形状仍与 DFT 的情况相似。然而，Bethe-Salpeter 方程（BSE）方法的谱整体形状与实验吻合较好。
