Modeling the optical properties of small gold nanoclusters using time-dependent density functional theory

摘要

The optical properties of gold nanoclusters of size 2-20 have been investigated using time-dependent density functional theory (TDDFT) to simulate their linear absorption spectra. Relativistic effects have been included by using pseudopotentials, with the Douglas-Kroll (DK) approximation, and with the zero-order regular approximation (ZORA). The improved model core potential with scaled relativistic effects (iMCP-SR2) used in combination with either the BP86, BLYP, or B3LYP exchange-correlation density functional was found to fairly accurately model the spectra of clusters for which measured spectra are available, although the all-electron ZORA method was best both for accuracy and computational efficiency. The effects on the optical properties of organic chromophores from coordination with small gold clusters were preliminarily studied. The extent of enhancement of the absorption properties is seen to depend on the size and structure of the gold cluster.