LCP-A2MC, Institute Jean Barriol, Université de Lorraine, 1 Bd Arago, F-57078 Metz, France.
Université Libanaise, Faculté de Sciences (I), LPE-Laboratoire de Physique et d'Electronique, Campus Rafic Hariri, Hadath, Beirut, Lebanon.
J Chem Phys. 2018 Aug 7;149(5):054106. doi: 10.1063/1.5030539.
Equilibrium crystal structures, electron band dispersions, and bandgap values of layered GaSe and InSe semiconductors, each being represented by four polytypes, are studied via first-principles calculations within the density functional theory. A number of practical algorithms to take into account dispersion interactions are tested, from empirical Grimme corrections to many-body dispersion schemes. Due to the utmost technical accuracy achieved in the calculations, nearly degenerate energy-volume curves of different polytypes are resolved, and the conclusions concerning the relative stability of competing polytypes drawn. The predictions are done as for how the equilibrium between different polytypes will be shifted under the effect of hydrostatic pressure. The band structures are inspected under the angle of identifying features specific for different polytypes and with respect to modifications of the band dispersions brought about by the use of modified Becke-Johnson (mBJ) scheme for the exchange-correlation potential. As another way to improve the predictions of bandgaps values, hybrid functional calculations according to the HSE06 scheme are performed for the band structures, and the relation with the mBJ results are discussed. Both methods nicely agree with the experimental results and with state-of-the-art GW calculations. Some discrepancies are identified in cases of close competition between the direct and indirect gap (e.g., in GaSe); moreover, the accurate placement of bands revealing relatively localized states is slightly different according to mBJ and HSE06 schemes.
通过密度泛函理论中的第一性原理计算，研究了具有四种多型的层状 GaSe 和 InSe 半导体的平衡晶体结构、电子能带色散和带隙值。测试了多种考虑色散相互作用的实用算法，从经验 Grimme 修正到多体色散方案。由于计算中达到了极高的技术精度，解决了不同多型的近乎简并的能量-体积曲线，并得出了关于竞争多型体相对稳定性的结论。根据静水压力对不同多型体平衡的影响，对预测进行了说明。从识别不同多型体特有的特征的角度检查能带结构，并根据交换相关势的修正 Becke-Johnson（mBJ）方案对能带色散进行修正。为了进一步提高带隙值的预测精度，根据 HSE06 方案对能带结构进行了混合泛函计算，并讨论了与 mBJ 结果的关系。这两种方法都很好地与实验结果和最先进的 GW 计算吻合。在直接带隙和间接带隙之间存在竞争的情况下（例如在 GaSe 中），存在一些差异；此外，根据 mBJ 和 HSE06 方案，揭示相对局域态的能带的精确位置略有不同。
