Ab initio quasiparticle energy calculations of Ge clusters using the $GW$ approximation

Ab initio quasiparticle energy calculations of Ge clusters using the $G W$ approximation

Erm Kikuchi, Soh Ishii, and Kaoru Ohno

Phys. Rev. B 74, 195410 – Published 13 November 2006

Abstract

First principles all-electron $G W$ calculations are carried out for ${Ge}_{n}$ $(n = 3 - 6)$ clusters. Although the eigenvalues obtained within the local density approximation of the density functional theory are far off the experiment data, the absolute values of $G W$ quasiparticle energy of the highest occupied molecular orbital and the lowest unoccupied molecular orbital are in good agreement with the experimental ionization potentials and electron affinities. For ${Ge}_{5}$ and ${Ge}_{6}$ , the change of atomic geometry between the neutral and anion clusters plays a significant role in reproducing the experimental electron affinity. We also show that relativistic effect is not very important for germanium clusters.