Effects of interstitial impurities (H, O, and He) on the structure and electronic properties of [formula omitted]–W: A density functional theory-based study

Abstract

The A15 structure of W, the β–W, exhibits better properties for spintronics applications than bcc α–W. Previous works found that impurities could stabilize β–W. It is therefore important to identify the role and effects of impurities in the material. Hence, we performed DFT-based calculations and investigated the effects of interstitial impurities (12.50% and 1.56% atomic impurity concentrations of H, O, and He) on the structural and electronic properties of β–W. We also investigated α–W for comparison. We found that the binding energy of O is more favored in β–W than in α–W. However, the cohesive energy per atom of β–W is higher than α–W only when there is 12.50% atomic concentration of O in the system. This suggests that O has the tendency to induce α–W-to-β–W transition at this concentration of O. We found that the binding energies of H in β–W are energetically more favorable than in α–W, but the cohesive energies per atom are higher in α–W. These results imply that it will require a larger amount of energy to form β–W with H as an impurity. We found no stable site for He. Interaction between impurities and W atoms induces structural changes and an increase in the electron density of states at the Fermi level which highlights the effects of impurities in β–W.