Ab initio study of intrinsic, H, and He point defects in hcp-Er

Abstract

Ab initio calculations based on density functional theory have been performed to determine the properties of self-interstitial atoms (SIAs), vacancies, and single H and He atoms in hcp-Er. The results show that the most stable configuration for a SIA is a basal octahedral configuration, while the octahedral (O), basal split, and crowdion (C) interstitial configurations are less stable, followed by the split ⟨0001⟩ dumbbell and tetrahedral configurations. For both H and He defects, the formation energy of an interstitial atom is less than that of a substitutional atom in hcp-Er. Furthermore, the tetrahedral interstitial position is more stable than an octahedral position for both He and H interstitials. The hybridization of the He and H defects with Er atoms has been used to explain the relative stabilities of these defects in hcp-Er.

Атомная структура систем Zr-He, Zr-vac, Zr-vac-He: расчет из первых принципов

“…Поэтому мы сравнили полученные нами результаты с данными тео-ретических работ, посвященных изучению энергетики систем матрица−вакансия−гелий, где в роли матрицы выступали ОЦК-(α-Fe, Cr, Mo, W, V, Nb, Ta) [6,18,30], ГЦК-(Ni, Cu, Ag, Pd) [18] и ГПУ-(Er, Sc, Y, Gd, Tb, Dy, Ho, Lu) [31][32][33] металлы. Вычисленные в этих работах энергии растворения гелия в кристалле с вакансиями имеют положительные значения, как и в нашем случае для Zr.…”

First-principles Study on the Properties of Point Defects in Hcp-Dy

“… is the total energy of a supercell calculated in the present work, which contains a self-interstitial Dy atom, N is the number of atoms in the perfect hcp computational cell, Dy  denotes the energy of a Dy atom in a perfect hcp-Dy crystal [5].…”

“…Er-H/Er-He systems [4,5]. A 4×4×4 supercell (96 atoms) was employed to investigate the point defects, and gamma-centered grids were used in hcp-Dy.…”

“…Interest in rare-earth hydrides has been stimulated in the last few years for several reasons [2][3][4][5][6]. As is well known, 3 He accumulates in the host metal as tritium decays via the reaction: T→ …”

“…Properties of self-interstitial atoms defects for some hcp structure metals have been calculated using Ab initio density functional theory calculations [4,5]. Yang et al have studied the properties of H and He defects in hcp Sc and Er, and they found that, both H and He defects, the formation energy of an interstitial atom is less than that of a substitutional atom, Furthermore, the T (tetrahedral) interstitial position is more stable than an O (octahedral) position for both He and H interstitials in hcp structure Sc and Er [4,5]. However, there are few studies on the properties of interstitial H atoms and He atoms in hcp Dy.…”