基于第一性原理研究H_(2)O分子在双相TiAl合金表面的吸附行为

Adsorption Behavior of H_(2)O Molecules on Surface of TiAl Alloy Based on First Principles

为研究电场作用对H2O分子在γ-TiAl和α_(2)-Ti_(3)Al表面的吸附行为影响,采用第一性原理方法对H_(2)O分子在γ-TiAl(111)和α2-Ti_(3)Al(0001)表面不同吸附位置的吸附能、态密度、几何结构、电荷布局进行分析。结果发现,H_(2)O分子在γ-TiAl(111)和α_(2)-Ti_(3)Al(0001)表面上的top Ti位置吸附最为稳定,但电场更容易促进H_(2)O分子与α_(2)-Ti_(3)Al(0001)表面的相互作用,即α_(2)-Ti_(3)Al更易与H_(2)O分子发生反应,从而优先形成Ti的致密氧化膜,致使α_(2)-Ti_(3)Al被保护。探究γ-TiAl和α_(2)-Ti3Al单相具有相同溶解速度的条件,对提升双相(γ-TiAl和α_(2)-Ti_(3)Al相)TiAl合金电解加工表面质量具有十分重要的意义。

In order to study the adsorption mechanism of H_(2)O molecules on γ-TiAl(111)and α_(2)-Ti_(3)Al(0001)surfaces by electric field,the adsorption energy,state density,geometric structure and charge layout of H_(2)O molecules at different adsorption positions onγ-TiAl(111)and α_(2)-Ti_(3)Al(0001)surfaces were analyzed by first principles method.The results showed that the adsorption of H_(2)O molecules was most stable at the top Ti position on theγ-TiAl(111) and α_(2)-Ti_(3)Al(0001)surfaces,but the electric field was more likely to promote the interaction between H_(2)O molecules and α_(2)-Ti_(3)Al(0001)surfaces,that is,α_(2)-Ti_(3)Al was more likely to react with H_(2)O molecules.Thus,the dense oxide film of Ti was preferentially formed,resulting in the protection of α_(2)-Ti_(3)Al.It is of great significance to explore the condition thatγ-TiAl and α_(2)-Ti_(3)Al single-phase have the same dissolution rate,and to improve the surface quality of the electrochemical machining of the biphase(γ-TiAl and α_(2)-Ti_(3)Al)TiAl alloy.