A Theoretical Study On Geometries And Electronic Structure Of Gold Clusters

Because of their abnormal physical and chemical behavior, transition metalclusters have been widely applied in material science, nanotechnology,microelectronics, physical chemistry, life science and so on. During the pastseveral decades, the rapid development in computer hardware and found of densityfunctional theory make first-principles calculations on geometries and electronicstructure of atom cluster come to reality. Gold is a unique element in that it hasvery large relativistic effect, which is larger than its neighbors and any otherelement. Gold clusters have been received considerable attention during the pastfew years. The interest originates mainly from the remarkable physical andchemical properties and applications as catalyst.To search and verify the origin about abnormal properties of gold clusters, weapply first-principles density functional theory to investigate geometries andelectronic structure of Au,(2≤n≤10) clusters.Firstly, we apply Gassian03 code to search lowest-energy geometries ofAu_n(2≤n≤10) cluster. The hybrid exchange-correlation function B3LYP andscalar relativistic effective core potential LANL2DZ are used. All the optimalgeometries of Au,(2≤n≤10) calculated by us are planar. Based onlowest-energy geometries present by us, we further investigate electronic structureof gold clusters. Odd-even oscillation effect occurs in the second difference of binding energy, Fermi energy and HOMO-LUMO gap, which are consist in resultsreported by others. The stabilization of even number clusters is superior to that ofodd number clusters, as is due to that in even number gold clusters the valuesdifference of binding energy and HOMO-LUMO Gap are large than those in theodd number clusters. Difference in stabilization firmly correlates to electron-paireffect in gold clusters.In order to obtain more exact results, another effort is applying DMOL codeto perform all electronic scalar relativistic calculation based on the lowest-energyfrom scalar relativistic effective core potential calculations. Then we discuss thedifferent between results from RECP and all electron calculations. We find that,including all electrons consideration, the average bond length contract about 3-5%,average binding energy expand about 3-5%, the second difference in bindingenergy almost keep unvarying., Fermi energy level expand 11%-15%, and energygap contract almost 50%. So we advise that the relative corrections must beconsidered in investigation of Au clusters if the RECP is adopted.The results come from two methods are consistent. All the optimalgeometries calculated by us are planar. Odd-even oscillation effect occurs in thesecond difference of binding energy, Fermi energy and HOMO-LUMO gap. Thestabilization of even number clusters is superior to that of odd number clusters, asis due to that in even number gold clusters the values difference of binding energyand HOMO-LUMO Gap are large than those in the odd number clusters.Difference in stabilization firmly correlates to electron-pair effect in gold clusters.