First-principles study for strain effects on oxygen migration in zirconium

Oxygen interstitial atom diffusion in bulk alpha-Zr is studied using first-principles calculation and nudged elastic band method under various tetragonal strain conditions. Octahedral site is a stable position for an oxygen interstitial in alpha-Zr. An oxygen interstitial atom may diffuse from one octahedral site to another via a tetrahedral site or a crowdion site. An oxygen atom can travel around zirconium bulk with various combination of these diffusion processes. The diffusion from an octahedral site to a tetrahedral site or a crowdion site is the controlled step. The strain effects on the two diffusion mechanisms are different. In general, the diffusion rate decreases under certain tetragonal compressive strain conditions. As a result, the oxidation rate decreases under certain compressive strain conditions. Since surface coating may be used to protect zirconium metal surface from oxidation, the surface strain generated from the interfacial mismatch can be used for the material design. In our calculations, SiC, TiN, and Al2O3 coatings may slow down the oxidation rate of zirconium because they can induce compressive strain on zirconium near the interfacial region. (C) 2017 Elsevier B.V. All rights reserved.