期刊
ACTA MATERIALIA
卷 59, 期 8, 页码 3214-3228出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2011.01.062
关键词
Magnesium alloys; Impurity diffusion; Density functional theory
资金
- National Science Foundation (NSF) [DMR-0510180, DMR-1006557]
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [1006557] Funding Source: National Science Foundation
- Office of Advanced Cyberinfrastructure (OAC)
- Direct For Computer & Info Scie & Enginr [821527] Funding Source: National Science Foundation
Diffusion in dilute Mg-X alloys, where X denotes Al, Zn, Sn and Ca impurities, was investigated with first-principles density functional theory in the local density approximation. Impurity diffusion coefficients were computed as a function of temperature using the 8-frequency model which provided the relevant impurity and solvent (Mg) jump frequencies and correlation factors. Minimum energy pathways for impurity diffusion and associated saddle point structures were computed with the climbing image nudged elastic band method. Vibrational properties were obtained with the supercell (direct) method for lattice dynamics. Calculated diffusion coefficients were compared with available experimental data. For diffusion between basal planes, we find DMg-Ca > DMg-Zn DMg-Sn DMg-Al, where D is the diffusion coefficient. For diffusion within a basal plane, the same trend holds except that DMg-zn overlaps with DMg-Al at high temperatures and DMg-sn at low temperatures. These trends were explored with charge density contours in selected planes of each Mg X alloy, the variation of the activation energy for diffusion with the atomic radius of each impurity and the electronic density of states. The theoretical methodology developed herein can be applied to impurity diffusion in other hexagonal materials. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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