Vacancy trapping behaviors of oxygen in tungsten: A first-principles study

We have investigated the interaction between oxygen (O) and vacancy in tungsten (W) using a first-principles simulation method. We show that a single O atom prefers to occupy a site of ∼1.28 Å off the vacancy center close to an octahedral interstitial site in W with a trapping energy of −3.05 eV. Multi O atoms in W exhibit a repulsive interaction at the vacancy, and a mono-vacancy can hold six and three O atoms via the "simultaneous way" and the "sequential way", respectively, without formation of the O2 or O3 molecule. We demonstrate that the stronger W–O bonds form when the O atoms segregate into the vacancy which is similar to the WO3 compound. All these results suggest the strong vacancy trapping characteristic of O in W