W掺杂对TiO2中氧空位形成能的影响

为研究Ti合金中常用的基体强化元素W对合金抗氧化性的作用,利用第一性原理方法计算了W掺杂对Ti合金氧化产物金红石TiO₂中氧空位形成能的影响。计算发现,W可以显著增大其近邻位置的氧空位的形成能,使其增大将近0.7 eV,这将有效抑制氧空位的产生以及环境中氧的渗透,对Ti合金的抗氧化性是有益的。同时研究了2个氧空位组成的不同构型的空位对,发现W同样可以增大氧空位对的形成能,但增加的数值平均到每个氧空位只有0.2 eV,即随着氧化的加剧和氧空位浓度的增加,W对抗氧化性能提高的效果减弱。电子态密度分析表明,对于不同构型的氧空位对,体系内的未配对电子分布在不同的能级水平,这导致了不同的空位形成能。

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.