Positron lifetime calculations for defects in Zn

Abstract

The effect of the lattice relaxation at vacancy clusters and interstitial-type dislocation loops on the lifetime of positrons in Zn has been studied. Defective relaxed structures have been generated for the lifetime calculations by using a many-body potential for Zn. From the results, it is inferred that the effect of the atomic relaxation is mainly significant for small vacancy clusters. The lifetime associated with interstitial-type loops is very sensitive to the loop structure and its surroundings. Previous experimental results are compared with the theoretical calculations.

Plastic Deformation of Nanocrystalline Zinc Investigated by Positron Annihilation Lifetime Spectroscopy

“…The lifetime 𝜏 1 is about 178 ps for the uncompressed bulk sample. The calculated bulk lifetime of Zn is about 158 ps, [16] and the experimental data reported in the literature are 152 ps, [16] 160 ps [9] and 165 ps. [11] Apparently, the lifetime 𝜏 1 of 178 ps is larger than all of them, but smaller than the positron lifetime 057804-2 in a monovacancy (220 ps in Ref.…”

“…[11] Apparently, the lifetime 𝜏 1 of 178 ps is larger than all of them, but smaller than the positron lifetime 057804-2 in a monovacancy (220 ps in Ref. [16]). This observation indicates that the polishing process has induced some defects into the surface zone of the bulk sample.…”

“…2 is much smaller than that of the bulk sample. On the one hand, according to the value of the lifetime 𝜏 2 (about 375 ps), vacancy clusters containing about ten monovacancies [16] are distributed in the sample. These defects hinder the diffusion of grain boundaries, and therefore plastic deformation becomes hard.…”

Исследование Вакансионной Системы Реструктурированного Цинка Методом Аннигиляции Позитронов

“…Время жизни данной компо-ненты изменяется от образца к образцу, что говорит о различном типе и размере дефектов, присутствующих в материале. Время жизни долгоживущей компоненты в образце Zn1 составляет 250 ps, что на 30 ps выше экспериментального значения времени жизни позитрона в вакансии цинка [19]. Это может говорить о том, что в Zn1 имеются дефекты в форме вакансионных кластеров.…”

First-principles calculations of positron lifetimes of lattice defects induced by hydrogen absorption

“…While lattice relaxation is not significant for positron lifetime calculations in the case of three-dimensional vacancy clusters composed of more than three vacancies [21], two-dimensional vacancy clusters may collapse to form dislocation loops accompanying large lattice relaxations. In order to take into account lattice relaxation in positron lifetime calculations, the relaxation around the two-dimensional V6 cluster on (111) plane is calculated using first-principles pseudopotential method as implemented in the Vienna ab initio simulation package (VASP) [22,23].…”