Investigation and calculation of positron lifetimes of monovacancies in crystals

The International Workshop on Positron Studies of Defects 2014

Huang, Shijuan^1,2 ; Liu, Jiandang^1,2 ; Ye, Bangjiao^1,2

State Key Laboratory of Particle Detection and Electronics (IHEPandUSTC), University of Science and Technology of China, Hefei

230026, China^1

Department of Modern Physics, University of Science and Technology of China, Hefei

230026, China^2

关键词: Atomic relaxation;    Calculation scheme;    First-principles calculation;    Monovacancies;    Neutral-charge;    Positron lifetime;    Two-component;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/674/1/012022/pdf
DOI  :  10.1088/1742-6596/674/1/012022

来源: IOP

【 摘 要 】

The first-principles calculations of positron lifetimes of mono-vacancies in crystals were investigated. We use the two-component density functional theory to respectively compute positron lifetimes of neutral charge state of VAldefect in aluminium, VSidefect in silicon, VC, VSiand VC+CSidefects in 3C silicon carbide, VGaand VAsdefects in gallium arsenide, taking into account atomic relaxation due to vacancy and electronic structural relaxation due to the presence of the positron. Three different calculation schemes are used. We find that the electron density inside the vacancy more or less increases due to the presence of the positron if the ionic positions are kept fixed, and the positron becomes more localized after the electronic structural relaxation for the case of VAldefect in aluminium and VSidefect in 3C silicon carbide, but it is opposite for the case of VGadefect in gallium arsenide and VCdefect in 3C silicon carbide. The results with no consideration of the relaxation are even much closer to the experimental ones, therefore the atomic relaxation due to the position play an important role in calculating the positron lifetime of mono-vacancies in crystals.