Mackrodt William C, Rérat M, Gentile F S, Dovesi R
Dipartimento di Chimica, Università di Torino, Via P. Giuria 5, 10125 Torino, Italy.
J Phys Condens Matter. 2020 Feb 20;32(8):085901. doi: 10.1088/1361-648X/ab4c0e. Epub 2019 Oct 8.
This paper reports calculated energies and electronic structures of O(2p), O(2s) and Al(2p) excited states in bulk [Formula: see text]-AlO, at the [Formula: see text] and [Formula: see text] surfaces and in the presence of O vacancy defects, obtained from all-electron HF, B3LYP, GGA and LDA calculations based on a recently described direct [Formula: see text]-SCF approach (Mackrodt et al 2018 J. Phys.: Condens. Matter 30 495901). The closely related frequency-dependent optical constants derived from B3LYP calculations within the CPHF/DF framework are also reported, where both sets of results are shown to compare favourably with the experimental spectra. The differences between the directly calculated excited state energies, which in [Formula: see text]-AlO are equal to the leading excitation edges, based on the four functionals, are substantially less than the differences between the corresponding (ground state) band gaps, as reported previously for AFII NiO (Mackrodt et al 2018 J. Phys.: Condens. Matter 30 495901). For the B3LYP functional, these energies are 8.7 eV, 12.5 eV and 73.7 eV for the O(2p), O(2s) and Al(2p) excitations respectively. The O(2p) edge is predicted to be degenerate, with distinct excitations from O(2p) states that are parallel to and perpendicular to the c-axis, in agreement with the reported spectra (Tomiki et al 1993 J. Phys. Soc. Japan 62 573). Detailed analyses of the charge and spin distributions in the four bulk excited states indicate that these are essentially charge-transfer excitonic, with acceptor sites at the nearest neighbour positions. Despite the close proximity of the O([Formula: see text]) and O(2p[Formula: see text]) excited state energies, the charge and spin distributions are predicted to be quite different.
本文报道了基于最近描述的直接(\Gamma)-SCF方法（Mackrodt等人，2018年，《物理：凝聚态物质》30卷，495901），通过全电子HF、B3LYP、GGA和LDA计算得到的体相(\alpha)-AlO、(\alpha)和(\beta)表面以及存在氧空位缺陷时O(2p)、O(2s)和Al(2p)激发态的计算能量和电子结构。还报道了在CPHF/DF框架内基于B3LYP计算得出的密切相关的频率依赖光学常数，两组结果均显示与实验光谱具有良好的可比性。基于这四种泛函直接计算的激发态能量（在(\alpha)-AlO中等于主要激发边缘）之间的差异，远小于相应的（基态）带隙之间的差异，如先前报道的AFII NiO（Mackrodt等人，2018年，《物理：凝聚态物质》30卷，495901）。对于B3LYP泛函，O(2p)、O(2s)和Al(2p)激发的这些能量分别为8.7 eV、12.5 eV和73.7 eV。O(2p)边缘预计是简并的，与报道的光谱一致（Tomiki等人，1993年，《日本物理学会杂志》62卷，573页），存在来自平行于和垂直于c轴的O(2p)态的不同激发。对四种体相激发态中的电荷和自旋分布的详细分析表明，这些本质上是电荷转移激子，受体位点位于最近邻位置。尽管O((\pi))和O(2p(\pi))激发态能量非常接近，但预计电荷和自旋分布会有很大不同。
