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首页> 外文期刊>Journal of Alloys and Compounds: An Interdisciplinary Journal of Materials Science and Solid-state Chemistry and Physics >Theoretical calculation of positron lifetimes for LaNi_5-H system
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Theoretical calculation of positron lifetimes for LaNi_5-H system

机译：LaNi_5-H系统正电子寿命的理论计算

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摘要

Positron lifetime spectroscopy is a powerful tool for the study of vacancy-type defects in solids. Our positron lifetime measurements have revealed that huge numbers of excess vacancies are formed in addition to dislocations during the first hydrogen absorption process of LaNi_5 and excess vacancies becomes mobile and form microvoids by a thermal activation process. For further investigation, theoretical approaches using electronic structure calculations are indispensable. In this work, we have performed theoretical calculations of positron lifetime for LaNi_5-H system using first principles electronic structure calculations. By comparison between the theoretical and experimental positron lifetimes, one of the defect components during hydrogen absorption can be ascribed to the annihilation at vacancy-clusters composed of two or three Ni vacancies. The positron lifetime of the vacancy-cluster component increases over 400 ps during isochronal annealing after hydrogen desorption. The vacancy-cluster may contain not only Ni vacancies but also La vacancies, since the vacancy-cluster composed of only Ni vacancies cannot yield such a long positron lifetime.
机译：正电子寿命谱是研究固体中空位型缺陷的有力工具。我们的正电子寿命测量结果表明，在LaNi_5的第一个氢吸收过程中，除了位错之外，还形成了大量的过量空位，并且过量的空位变得可移动并通过热活化过程形成微孔。为了进一步研究，使用电子结构计算的理论方法是必不可少的。在这项工作中，我们已经使用第一原理电子结构计算对LaNi_5-H系统进行了正电子寿命的理论计算。通过比较理论和实验的正电子寿命，可以将氢吸收过程中的一种缺陷成分归因于由两个或三个镍空位组成的空位簇的an灭。在氢脱附后的等时退火过程中，空位簇组分的正电子寿命增加了400 ps以上。空位簇不仅可以包含Ni空位，还可以包含La空位，因为仅由Ni空位组成的空位簇不能产生如此长的正电子寿命。

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