Density Functional Theory Studies Of The Interaction Between Gold Cluster And Organic Molecules

Because of their novel physical and chemical behavior,transition metal clusters have been widely applied in material science, nanotechnology, microelectronics, physical chemistry,life science and so on. Gold is a unique element in that it has very large relativistic effect. Gold clusters have been received considerable attention during the past few years. The interest originates mainly from the remarkable physical and chemical properties and applications as catalyst. There are several reactions that can occur on nanoparticles, such as catalysis, corrosion, coating, etc. Because adsorption will be involved in the first step of the reactions, the adsorption of small molecules onto nanoparticles has been quite widely studied.The adsorptions among Au_3,5⁺clusters and CH₃OH molecules have been investigated using density functional theory. The geometric parameters, vibrational frequencies, adsorption energies and Mulliken charges are used to analyze the interactions between Au_3,5⁺ clusters and methanol molecules. The present calculations show that more than one methanol molecule can be adsorbed onto small clusters of gold ions, and that this adsorption is different from that of single molecule absorption. The red shift of C-O stretching frequency decreases as the number of methanol molecules m increases, or as gold cluster size increases. The positive charge on Au_3,5⁺ and the coordination number of the adsorption sites on the gold cluster are the dominant factors responsible for the strength of the interactions. We have obtained C-O stretching frequencies in Au_1,2⁺-(CH₃OH) complexes that are below 931 cm-1, which provides theoretical basis for the experimental observation by Dietrich et al.The interactions of acetone molecules with Au3 and Au5 clusters have been investigated. The geometries, adsorption energies and deformation electron density distributions were used to analyze these interactions. The present calculations show that several acetone molecules can be adsorbed on small gold clusters. Moreover, these adsorptions are obviously different from the cases that only one acetone molecule is adsorbed. It is found that the coordination number of the adsorption site on gold cluster is responsible for the strength of interactions. The effects of the Au-O bond lengths on adsorption energies between Au clusters and acetone molecules are also examined.