Effects of W-doping on formation energy of oxygen vacancy in TiO₂

First-principles calculations were used to study the influence of W-doping on the formation energy of oxygen vacancy in rutile TiO₂ oxide, in order to explore the possible effects on the corrosion resistance of Ti alloys by the addition of W which is normally used to strengthen the matrix. It was found that W can increase the formation energy of neighboring oxygen vacancy by nearly 0.7 eV, meaning that it can inhibit the generation of oxygen vacancy and the penetration of oxygen into the matrix effectively, which is beneficial for the oxidation resistance of Ti alloys. For the oxygen-vacancy pairs with different configurations, W can also increase their formation energy, by only 0.2 eV per vacancy; therefore, the positive effects of W will be weakened with the accumulation of oxygen vacancies and the acceleration of the oxidation process. Analysis on the electronic density of states shows that for oxygen-vacancy pairs with various configurations, the energy levels of the states of the unbounded electrons are different, which eventually lead to various formation energies.