铯在钨(110)表面吸附行为的第一性原理研究

通过基于密度泛函理论的第一性原理计算方法，研究了铯原子在钨(110)表面上的吸附行为。计算结果表明，通过原子数之比定义的最大单层铯原子吸附率为0.4，铯原子的吸附位置随吸附率的增加而变化。铯原子吸附率为0.25时，最可能的吸附位置是长桥，而铯原子吸附率达0.4时，铯原子在钨(110)表面形成完整的单原子层，并呈现-ABA′B′-结构形式。随铯原子吸附率的增加，表面功函数先减小后增大，最终稳定在2.134 eV，其中最小值1.524 eV出现在吸附率为0.25时，该最小值低于纯铯(110)表面的功函数。偶极子模型和分态密度计算结果表明，铯原子向钨基体表面的电子转移机制和铯原子电子能量分布的变化是造成表面功函数降低的原因。

The First Principle Study of Cesium Adsorption Behavior on Tungsten (110) Surface

Through the first principle calculation based on density functional theory (DFT), the cesium adsorption behavior on tungsten (110) surface was investigated. The calculation results show the maximum cesium adsorption rate defined by relative atom number of a monolayer is 0.4, and the cesium adsorption location alters with the increase of adsorption rate according to the adsorption energy calculation. The long bridge location is the most likely adsorption position for cesium atom at the adsorption rate of 0.25. A new surface adsorption periodic structure of-ABA′B′-style appears and the adsorbate forms a complete monolayer when the adsorption rate is 0.4. As the cesium adsorption rate increases, the work function decreases at first and then increases until reaching a plateau of 2.134 eV. The work function minimum value of 1.524 eV appears at the adsorption rate of 0.25, lower than work function of pure cesium (110) surface. The calculation results of the dipole model and partial density of state (PDOS) show that the mechanism of electron transfer from cesium atom to tungsten surface and the change of electron energy distribution contribute to the decrease of surface work function.