Ag在MgF2(010)表面吸附的密度泛函理论研究

基于密度泛函理论(DFT)的第一性原理赝势法, 对MgF2(010)面及吸附Ag的构型进行了优化, 并计算了MgF2(010)面吸附Ag体系的吸附能、 电子结构和光学性能. 结果表明, MgF2(010)面能隙低于体相, 态密度分裂, 出现表面态. Ag在MgF2(010)面的吸附属于稳定的化学吸附, 最佳吸附位为最外层F的四重穴位. 吸附机理主要表现为Ag的4p轨道与第二层的Mg的2p和3s轨道之间发生相互作用, 有少量电荷从Ag向Mg迁移. 吸附Ag后, 可见光波段的光吸收增加, Ag吸附后将使体系在可见光波段出现吸收峰.

Density Functional Theory Study on Ag Adsorption on MgF2 (010) Surface

Geometric and electronic structures of MgF2(010) surface were calculated by the ultra-soft pseudo-potential plane wave method based on density functional theory(DFT).Furthermore,the adsorption of Ag on the surface was discussed.The results show that compared with MgF2 bulk,the band gap of MgF2(010) surface is narrowed by about 0.9 eV,the energy state is split and there appear surface states,which is due to the dangling bonds of atom F of the first layer.Also,it is found that the density of state(DOS) of the top layer F is higher than that of the bulk,which indicates that the surface is active and it is easy to interact with outside.Calculations of Ag adsorption on the MgF2(010) surface show that the 4-fold hollow is energetically favorable and the adsorption is chemical.The analysis on the adsorption mechanism reveals that the electronic transfer mainly occurs between 4p of Ag and 2p and 3s of Mg.The discussion about optical property shows that the absorption in the visual band has a significant increase,which will definitely influence the optical properties of Ag/MgF2 multilayer.