氧在Nb(110)表面吸附的第一性原理研究

通过第一性原理赝势平面波方法研究了氧在Nb(110)表面的吸附性质随覆盖度变化规律. O在Nb(110)表面最稳定吸附位是洞位,次稳定吸附位是长桥位. 在长桥位吸附时, O诱导Nb(110)表面功函数随覆盖度的增加而几乎线性增加；但当O在洞位吸附时, 与干净Nb表面相比, 覆盖度为0.75 ML和1.0 ML时功函数增加, 而覆盖度为0.25 ML和0.5 ML时功函数减小.通过对面平均电荷密度分布和偶极矩变化的讨论, 解释了由吸附导致功函数复杂变化的原因.通过对表面原子结构和态密度分析, 讨论了O在Nb表面吸附时引起表面原子结构变化以及O和Nb(110)表面原子的相互作用.

Oxygen adsorption on Nb(110) surface by first-principles calculation

The adsorption of atomic oxygen on the Nb(110) surface is systematically investigated through the first-principles method for oxygen coverage ranging from 0.25 to 1 monolayer(ML).It is found that the hollow site is the most energetically favorable for the whole coverage range considered and that the long-bridge site takes the second place.The work function increases almost linearly with the increase of oxygen coverage for the long-bridge site adsorption,whereas for the hollow site adsorption the work function decreases when the coverage is 0.25 ML or 0.5 ML and increases when the coverage is 0.75 ML or 1 ML.Using the planar averaged charge density and the dipole moment change we can explain the complicated change of work function induced by atomic oxygen adsorption.In addition,the interaction between O and Nb is analyzed by the surface atomic structure and electronic density of states.