Structure and electronic excitation spectra of low-lying isomers of Aun clusters (n = 2–20). A DFT study

Abstract

The global structure optimization using the DFT-calibrated empirical potentials followed by the geometry optimization at the DFT level (BPW91/LANL2DZ) has been carried out in order to locate the low-lying isomers of Aun clusters (n = 2–20) modeling the sub-nanoparticles of the photocatalytic composite materials. The total energies, thermodynamic parameters and electronic properties of the located global and low-lying structures of various multiplicities are estimated, and their dependence on the nuclearity and cluster morphology are discussed. For the low-lying isomers, the electronic excitations spectra were calculated at the CAM-B3LYP/LANL2DZ level, and the electronic density redistribution during the excitations were analyzed. This analysis demonstrates that the planar clusters have the highest absorption ability and, at the same time, are the favorable structures for the intermolecular charge redistribution.