完美晶体中正电子体寿命计算的几种方法的分析与比较  

Anylasis and comparison of several methods for calculation of positron bulk lifetime in perfect crystals

作　　者：黄世娟[1,2] 张文帅[1,2] 刘建党[1,2] 张杰 李骏[1,2] 叶邦角[1,2] 

机构地区：[1]中国科学技术大学,核探测器与核电子学国家重点实验室,合肥230026 [2]中国科学技术大学近代物理系,合肥230026 [3]中科院等离子体物理所,合肥230026

出　　处：《物理学报》2014年第21期364-373,共10页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11175171,11105139)资助的课题~~

摘　　要：以正电子寿命为探测对象的正电子湮没寿命谱技术在研究半导体等材料的微缺陷方面得到了广泛的应用,它对晶体的结构类型、缺陷种类以及温度等十分敏感,因此,理论上正电子寿命的快速精确计算与实验数据的结合分析显得尤为重要.采用中性原子叠加模型、赝势方法和全势方法处理正电子局域势能,有限差分方法自洽求解正电子波函数,局域密度近似和广义梯度近似处理正电子电子关联势和增强因子,以体心立方结构的α-Fe、面心立方结构的Al和复式面心立方结构的Si三种单晶固体为例,分别计算了它们的正电子体寿命,计算值与相应的实验结果和其他计算结果均符合较好.同时细致分析了这几种方法在电子密度网格点精度、正电子电子关联势和增强因子等方面对正电子体寿命计算的影响,探讨了这几种方法在计算正电子体寿命方面各自的优缺点.Positron annihilation lifetime spectroscopy, which takes positron lifetime as a detected object, has been widely applied to the study on micro-defects of semiconductors and other materials, and is very sensitive to the type of crystal structure, defect types, and temperature, and so on. Therefore, the analysis of fast and accurate calculation of positron lifetime theoretically combined with the experimental data is particularly necessary. In this paper, the superposed neutral atom model, the pseudo-potential model, and the full-potential model are used to deal with the positron local potential.While the positron wave function is solved self-consistently by the finite difference method, the positron-electron correlation potential and its enhancement factor are handled within the frame work of the local density approximation and the generalized gradient approximation. We have respectively calculated the positron bulk lifetime of three kinds of single crystal solid： the alpha iron of a body-centered cubic structure, the aluminum of a face-centered cubic structure, and the silicon of a double face-centered cubic structure. Calculation results agree well with the published experimental data.At the same time, the impact on positron bulk lifetime due to electron density grid point accuracy, positron-electron correlation potential and enhancement factor is analyzed carefully. Finally, we discuss the advantages and disadvantages of the three methods for calculating the positron bulk lifetime. In summary, an effective and reasonable calculation for the positron bulk lifetime should take into account the electron density, positron-electron correlation potential, and enhancement factor, etc. especially the enhancement factor.

关 键 词：正电子体寿命 完美晶体 正电子电子关联势 增强因子 

分 类 号：O572.322[理学—粒子物理与原子核物理]