摘要
基于局域密度近似的密度泛函理论,运用多体摄动理论的GW近似,计算了碱金属锂的卤族化合物LiF (001)-(1X1)、LiCl (001)-(1X1)、LiBr (001)-(1X1)、LiI (001)-(1X1)表面的准粒子能带结构.GW近似改进了密度泛函理论对于电子交换关联的处理,计算出的带隙与实验值吻合.由GW近似计算得出的LiF、LiCl和LiBr的(001)表面能带具有负亲和能,由于绝缘体表面外真空中电子与绝缘体表面极化电荷的相互作用,在真空中产生了镜像势态.利用GW近似研究了镜像势态波函数沿表面法线方向的分布,并将由GW近似计算得到的镜像势态的单粒子势能与经典的镜像势能进行了比较.但是,从GW近似给出的表面能带结构可看出,LiI(001)表面具有正亲和能,因而不存在镜像势态.
Based on density functional theory concerning the local-density approximation(LDA), the multiplebody perturbation theory regarding the GW approximation(GWA) is used to calculate the band structures for the surfaces of alkali metal halides including LiF(001)-(1X1), LiCl(001)-(1X1), LiBr(001)-(1X1) and LiI(001)-(1X1). Since the GWA improves the electronic exchange-correlation within the LDA, the obtained GWA band gaps are in good agreement with the corresponding experimental results. It is found that the surface of LiF(001)-(1X1), LiCl(001)-(1X1), and LiBr(001)-(1X1) has negative electron affinity, and the image-potential state exists in the vacuum outside the surface, which results from the electrostatic interaction between an electron outside the surface and the polarizability in the insulator. The distributions of the wave functions for the image-potential states along the directions perpendicular to the surfaces are investigated, and the calculated local potentials using the GWA are compared with the corresponding classical image potentials. It is worth noting that since LiI(001) is not a negative electron affinity surface, there is no image-potential state existing in the vacuum outside the LiI(001) surface.
引文
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