Molecular dynamics study of hydrogen-vacancy interactions in α-zirconium

Hydrogen is known to have detrimental effects on the mechanical properties of zirconium and its alloys, mainly due the formation of brittle hydride phases. The behaviour of hydrogen dissolved in zirconium is not fully understood at the atomic scale. In particular, the influence of hydrogen on the behaviour of defects in zirconium still needs to be clarified. In this paper, we report a molecular dynamics study of hydrogen behaviour in zirconium using an improved Zr-H interatomic potential. We determined the diffusivity of hydrogen in zirconium, and the interaction of hydrogen atoms with a single or a pair of atomic vacancies. The computed hydrogen diffusion is found to be in good agreement with experimentally determined values. Our results also indicate that hydrogen interactions with vacancies in zirconium promote vacancy clustering. Moreover, hydrogen is found to substantially decrease the mobility of divacancies. From the present simulation findings, it is concluded that the presence and concentration of hydrogen impurities may have a significant influence on the evolution of irradiation-induced defects in zirconium alloys.