Electronic and structural effects of vacancies and substitutional O impurities in beta-tungsten: A density functional theory study

Abstract

In this study, we investigated the effects of vacancy and O substitutional defects on beta-W (β−W) by performing density functional theory (DFT)-based calculations. We focused on the changes in the stability, structural, and electronic properties of the system in the presence of defects. We also examined the stable alpha-W (α−W) for comparison. Our results reveal that for systems with vacancy defect, α−W is more energetically favorable than β−W. Meanwhile, significant structural deformations take place in β−W upon introducing O impurity on the face site. We note that with O as dopant, the cohesive energy of β−W becomes more favorable than the α−W which suggests the tendency of O to induce α−to-β−W transformation. Charge analysis revealed that charge transfer process governs the interaction between O and W in which O gains charge from the neighboring W atoms. Furthermore, the stronger interaction of O with W atoms of β−W than with α−W confirms the stabilization of β−W in the presence of O impurity.