title: Ab initio study of stability and migration of H and He in hcp-Sc.
abstract: Ab initio calculations based on density functional theory have been performed to determine the relative stabilities and migration of H and He atoms in hcp-Sc. The results show that the formation energy of an interstitial H or He atom is smaller than that of a corresponding substitutional atom. The tetrahedral (T) interstitial position is more stable than an octahedral (O) position for both He and H interstitials. The nudged elastic band method has been used to study the migration of interstitial H and He atoms in hcp-Sc. It is found that the migration energy barriers for H interstitials in hcp-Sc are significantly different from those for He interstitials, but their migration mechanisms are similar. In addition, the formation energies of five different configurations of a H-H pair were determined, revealing that the most stable configuration consists of two H atoms located at the second-neighbor tetrahedral interstitial sites along the hexagonal direction. The formation and relative stabilities of some small He clusters have also been investigated.
authors.affiliation: Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054, People's Republic of China. yanglildk@uestc.edu.cn
authors.forename: L
authors.initials: L
authors.lastname: Yang
authors.forename: S M
authors.initials: SM
authors.lastname: Peng
authors.forename: X G
authors.initials: XG
authors.lastname: Long
authors.forename: F
authors.initials: F
authors.lastname: Gao
authors.forename: H L
authors.initials: HL
authors.lastname: Heinisch
authors.forename: R J
authors.initials: RJ
authors.lastname: Kurtz
authors.forename: X T
authors.initials: XT
authors.lastname: Zu