A THEORETICAL STUDY OF CHLORINE MOLECULE ADSORPTION ON Au CLUSTERS

Abstract

Adsorption of chlorine molecule on cationic, neutral, and anionic Aun (n=1−6) clusters have been studied using density functional theory to find the adsorption structure and energy, charge population, and vibrational frequency. Comparative results are obtained using the PW91 exchange-correlation functional and the B3LYP hybrid functional. Calculations show a pronounced sensitivity to cluster size and charge state. Adsorption energy of Cl2 is above 0.2 eV on all clusters, indicating that the adsorption is energetically favorable. The adsorption energies of cationic clusters decrease as the cluster size increases. An even-odd oscillation of the adsorption energy is observed for neutral clusters, in which the odd clusters were observed to favor dissociative adsorption. Adsorption energy for the anionic clusters was found to be consistently high in the range of 2.4 - 4.5 eV with the exception of Au3－ cluster. Effects of the strength of interaction between Cl2 and Aun on charge transfer and Cl-Cl stretching frequency are also discussed. In addition Au3Cl2 cluster showed an extraordinary stability amongst the studied clusters which was further explained based on structural planarity, binding energy of Cl2 molecule on the clusters and energetics of its nearest neighbours. Our results demonstrate the possibility of electronic structure engineering by cluster size control.