Influence of dopants Cu, Ga, In, Hg on the electronic structure of CdnSn (n=6, 15) clusters - a DFT study

摘要

The influence of doping metal ions on the structural, electronic and optical properties of Cdn-yXySn (n - 6, 15; y = 1, 2, 4) clusters is systematically studied using DFT and TD-DFT studies. Among the dopants, Cu2+ and In2+ slightly distort the structure of CdnSn clusters, though they have a strong bonding interaction with S2- however; another two dopants Ga2+ and Hg2+ significantly distort the cluster's structure. Molecular composition analysis reveals the dopants not only contribute to the optically active states, but also to the surface or trap states. The HOMO-LUMO gap is significantly reduced for Cu2+, Ga2+, and In2+ dopants. However, for Hg2+ the gap is meagerly affected. In large clusters, Cd15S15, the polarizability values decrease on doping, though individual dopants show a nonlinear pattern. The absorption spectra of doped CdS clusters are generally red shifted though a few Ga and In clusters exhibit a blue shift due to the Burstein-Moss effect.