First-principle Studies On The Physical Properties Of Copper-based Transition Metal Clusters

Cluster is an aggregate of atoms or molecules in nano-scale size, containing anumber of constituent particles ranging from several to107. It is a new condensedmatter between microcosmic atom and macroscopical solid. There has been a greatattention for clusters' special geometric construction, peculiar characteristics inphysics and chemistry, and great foreground. The further study of clusters couldcontribute to improving the design and modification of microcosmic materials. Cuclusters have huge application prospects in catalysis, nanomaterials, energy reserves,large scale integrated circuit (LSI) producing, and new energy batteries' material.Therefore, in recent years, the researches on the Cu clusters have been hot topic fieldsand many achievements have been obtained.In this paper, we have studied geometric and electronic structures for neutral andcharged (positively and negatively) Cu38clusters through first-principle theorycombined with genetic algorithm (GA). Firstly, we do lots of work in global searchand study for geometric structures of Cu38by combining GA with Gupta potentialmethod, then we get a number of low-energy structures of Cu38, taking them asinitial structures, we make a progress in geometry optimization using DMol3packagewhich based on Density Functional Theory (DFT). Finally, we get the most stable(ground state) structure and some sub-stable structures. We analyze and discussgeometric structures, binding energies, HOMO-LUMO gaps, ionization potential andelectron affinity and so on.By simulating calculation, analyzing and summing up, main conclusions are asfollows.1. Although the results of structures and energies are different between GA andDFT, even the stability orders in structure are different. GA has its own advantages.GA can provide large numbers of low-energy structures in a short time. Taking thesestructures as candidates, we make relaxation in geometry optimization using DMol3package which based on Density Functional Theory (DFT). By combining GA andDFT, we can find ground state structure efficiently and accurately. The geneticalgorithm combined with first-principles calculations can still be effective in dealingwith structure optimization and study of midsize clusters.2. DFT calculation for neutral and charged Cu38clusters indicates three importantpoints.(1) Electrification can apparently affect the stability of clusters.(2) In the case of neutral clusters, the energies of OH and IMI structures are not so far different; theyare regarded as isomers with Cu38clusters. Compared with photoelectron spectrum,both of structures can been supposed to near-degenerate ground states of Cu38clusters.(3) The calculated ionization potential and electron affinity are in agreement with theexperimental observations.