Ab initio calculations for the neutral and charged O vacancy in sapphire

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	Ab initio calculations for the neutral and charged O vacancy in sapphire
	Xu YN ; Gu ZQ ; Zhong XF ; Ching WY
刊名	physical review b
	1997
卷号	56 期号:12 页码:7277-7284
关键词	OPTICAL-ABSORPTION CORUNDUM CRYSTALS ALPHA-ALUMINA F+ CENTER ALPHA-AL2O3 AL2O3 DEFECTS SIMULATION DAMAGE STATES
ISSN号	0163-1829
通讯作者	xu yn univ missouridept physkansas citymo 64110.
中文摘要	the energetics, lattice relaxation, and the defect-induced states of st single o vacancy in alpha-al2o3 are studied by means of supercell total-energy calculations using a first-principles method based on density-functional theory. the supercell model with 120 atoms in a hexagonal lattice is sufficiently large to give realistic results for an isolated single vacancy (square). self-consistent calculations are performed for each assumed configuration of lattice relaxation involving the nearest-neighbor al atoms and the next-nearest-neighbor o atoms of the vacancy site. total-energy data thus accumulated are used to construct an energy hypersurface. a theoretical zero-temperature vacancy formation energy of 5.83 ev is obtained. our results show a large relaxation of al (o) atoms away from the vacancy site by about 16% (8%) of the original al-square (o-square) distances. the relaxation of the neighboring al atoms has a much weaker energy dependence than the o atoms. the o vacancy introduces a deep and doubly occupied defect level, or an f center in the gap, and three unoccupied defect levels near the conduction band edge, the positions of the latter are sensitive to the degree of relaxation. the defect state wave functions are found to be not so localized, but extend up to the boundary of the supercell. defect-induced levels are also found in the valence-band region below the o 2s and the o 2p bands. also investigated is the case of a singly occupied defect level (an f+ center). this is done by reducing both the total number of electrons in the supercell and the background positive charge by one electron in the self-consistent electronic structure calculations. the optical transitions between the occupied and excited states of the: f and f+ centers are also investigated and found to be anisotropic in agreement with optical data.
学科主题	半导体物理
收录类别	SCI
语种	英语
公开日期	2010-11-17
内容类型	期刊论文
源URL	[http://ir.semi.ac.cn/handle/172111/15137]
专题	半导体研究所_中国科学院半导体研究所（2009年前）
推荐引用方式 GB/T 7714	Xu YN,Gu ZQ,Zhong XF,et al. Ab initio calculations for the neutral and charged O vacancy in sapphire[J]. physical review b,1997,56(12):7277-7284.
APA	Xu YN,Gu ZQ,Zhong XF,&Ching WY.(1997).Ab initio calculations for the neutral and charged O vacancy in sapphire.physical review b,56(12),7277-7284.
MLA	Xu YN,et al."Ab initio calculations for the neutral and charged O vacancy in sapphire".physical review b 56.12(1997):7277-7284.