Content area
Full text
Abstract
First-principle calculations were carried out to investigate the adsorption of CO over Cu nanoclusters. The structural, spectroscopic and electronic properties like optimized geometries, HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energy levels, binding energy, adsorption energy, vibrational frequency and density of states (DOSs) of the pure Cun nanoclusters, and Cu CO complexes in their ground state were thoroughly analyzed. The CO adsorbed on the Cu nanoclusters showed a stretch frequency at 1950-2052 cm-1, which was red-shifted relative to that of gas-phase CO (2143 cm-1). This red-shift was believed to arise from the charge transfer from the Cu metal d states to the CO antibonding 2n· level. The CO adsorption on the Cu nanoclusters was chemisorption in nature with the Cu-C bond length (adsorption height) in the range of 1.85-1.92 Å.
Keywords: B3LYP; CO adsorption; Cu nanoclusters; DOS; LanL2DZ.
(ProQuest: ... denotes formulae omitted.)
INTRODUCTION
Nanoclusters are of great scientific interest in fundamental science and industrial applications as they are, in effect, a bridge between bulk materials and atomic or molecular structures [13]. They have size-dependent properties such as tailoring of optical gap, unusual magnetism, and enhanced catalytic activity. However, a bulk material should have constant physical properties regardless of its size [4, 5]. The nanoclusters of Cu and other transitional metals have attracted the attention of not only chemists and physicists but also biologists, computer scientists, electronic engineers, and metallurgists. They have potential applications in microelectronics, photovoltaics, imaging and display technologies, sensing devices, thin film coating, molecular electronics, and catalysis [6, 7].
Copper has been identified as an important catalytic agent for carbon monoxide, CO, and oxidation [8]. Metal clusters have been proposed as molecular model systems for the chemisorption on extended metal surfaces. The similarity between a metal surface and small metal clusters that typically only contain between 2 and 10 atoms has been theoretically useful to gain insight into interactions between a metal center and organic or inorganic reactants [9]. The CO molecule is one of the most widely studied ligands in metal cluster chemistry as well as metal surface science. CO is a very suitable probe molecule to characterize the different binding sites on catalytic surfaces [10, 11]. The CO adsorption on several Cu systems has...