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Title: Ab initio study of stability and migration of H and He in hcp-Sc

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 atomss 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 that their migration mechanisms are similar. In addition, the formation energies of five different configurations of a He-He pair were determined, revealing that the most stable configuration consists of two He atoms located at the second-neighbor tetrahedral interstitial sites along the c axis. The formation and relative stabilities of some small He clusters have also been investigated.
Authors:
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Publication Date:
OSTI Identifier:
1004803
Report Number(s):
PNNL-SA-76726
Journal ID: ISSN 0953-8984; JCOMEL; AT6020100; TRN: US201104%%1111
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physics. Condensed Matter, 23(3):035701; Journal Volume: 23; Journal Issue: 3
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ATOMS; CONFIGURATION; FUNCTIONALS; INTERSTITIALS; STABILITY Ab initio calculations; hydrogen; helium; hcp-Sc