Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering, Peking University, 100871 Beijing, China.
J Chem Phys. 2013 Oct 28;139(16):164114. doi: 10.1063/1.4826321.
The ionization potential is the key to determine the absolute positions of valence and conduction bands of a semiconductor with respect to the vacuum level, which play a crucial role in physical and chemical properties of surfaces and interfaces. In spite of its far-reaching significance, theoretical determination of ionization potentials has not attained as much attention as that of band gaps. In this work, a set of prototypical semiconductors are considered to establish the performance of the state-of-the-art first-principles approaches. We have shown that in general Kohn-Sham density functional theory with local density approximation or generalized gradient approximation (LDA/GGA) significantly underestimates the ionization potentials of semiconductors. When the quasi-particle correction from many-body perturbation theory in the GW approximation is taken into account, the agreement between theory and experiment can be greatly improved. We have made a critical comparison between two GW correction schemes, one taking into account the GW correction to the valence band maximum (VBM) of the bulk system, and the other based on the assumption that the LDA/GGA gives correct band gap center (BGC). Our study shows that the VBM scheme is better founded theoretically and leads to closer agreement with experiment practically than the BGC scheme. For semiconductors with shallow semicore states, for which the band gaps from the GW approach also exhibit significant errors, there is still significant discrepancy between GW and experiment, indicating the necessity to go beyond the standard GW approach for these materials.
电离势是确定半导体价带和导带相对于真空能级的绝对位置的关键，这对表面和界面的物理和化学性质起着至关重要的作用。尽管它意义深远，但理论上确定电离势的研究并没有像研究能带隙那样受到重视。在这项工作中，我们考虑了一组典型的半导体来建立最先进的第一性原理方法的性能。我们表明，一般来说，局域密度近似或广义梯度近似（LDA/GGA）的 Kohn-Sham 密度泛函理论会严重低估半导体的电离势。当考虑 GW 近似中的多体微扰理论的准粒子修正时，理论和实验之间的一致性可以大大提高。我们对两种 GW 修正方案进行了批判性比较，一种考虑了体系统的价带最大值（VBM）的 GW 修正，另一种则基于 LDA/GGA 给出正确的能带隙中心（BGC）的假设。我们的研究表明，VBM 方案在理论上更有根据，并且在实践上与实验的一致性比 BGC 方案更好。对于具有浅半芯态的半导体，GW 方法的能带隙也表现出显著的误差，GW 和实验之间仍然存在显著的差异，这表明对于这些材料，需要超越标准的 GW 方法。
