Structural changes induced upon charging Ge clusters

Abstract

The geometries and electronic structures of neutral and charged ${\mathrm{Ge}}_{\mathrm{n}}$ clusters (n\ensuremath{\leqslant}10) are investigated using Langevin molecular dynamics coupled to a simulated annealing procedure. These calculations utilize quantum forces derived from ab initio pseudopotentials constructed within the local-density approximation, and are performed in real space using the higher-order finite difference method. The energy gaps, binding and fragmentation energies, and electron affinities are calculated, and good agreement is obtained with experimental data. Upon charging the clusters negatively, it is observed that the ground-state structure may significantly change in comparison to the neutral case. This observation explains the substantial difference in the photoemission spectra of ${\mathrm{Si}}_{10}^{\mathrm{\ensuremath{-}}}$ and ${\mathrm{Ge}}_{10}^{\mathrm{\ensuremath{-}}}$ clusters.