Structure Evolution And Relativistic Effects Of Small Gold Clusters

In recent years,gold nano systems have led to a lot of attention duing to their special structure and the application in catalyst.The preparation of helical Au nanotubes,the ground-state structure of tetrahedral,pyramidal Au₄₂ and the experimental results on the ground-state struture of Au₂₄ have attracted much interest.In particular,the theoretical predict on the ground-state structure of aromatic gold fullerene Au₃₂ set off the wave on the studies of gold fullerenes and nanotubes;the theoretical results on the ground-state of gold fullerene Au₅₀,fulfilling the 2(k+1)² criterion of spherical aromaticity and chiral,I-symmetric Au₇₂ have been reported.Relativistic effects of heavy metal lead to the 2D structure and the cage structure for small Au clusters.At present,this is still a open question on the evolvement of gold culsters as the culster size;the relationship between rules of the structure and internal electronic structure and the physical interpretation for the impact of relativstic effects on the track hybrid still need to be further excavated.The thesis studies of geometric,electronic properties and size dependence of Cu_n,Ag_n and Au_n(n=2-16) clusters which based on the density functional theory(DFT).Two main computational methods with DMol³ package and Gaussian-based are employed. Self-consistent-field(SCF) electronic structure calculation based upon the spin-polarized relativistic all-electron density functional theory(DFT) with based relativistic semi-core pseudopotentials(DSPP) is employed.The electronic exchange-correlation energy is treated under the generalized gradient approximation(GGA) corrected-exchange potential of the Perdew and Wang(Pw91).A double-numerical-polarization(DNP) basis set and the spin unconstrained are chosen to do the electronic structure calculation.Another density functional theory(DFT) based at a GGA level with Becke3 with Perdew-Wang 91(B3PW91) and LANL2DZ effective core basis set are chosen to do the electronic structure calculation.We analyzed the influence of relativistic effects to geometric,electronic properties of gold clusters.The result shows that:(1)The binding energy(E_b) increases with cluster size.Second order difference and HOMO-LUMO gap exhibits an obvious odd-even oscillation behavior on increasing with cluster size.(2)The HOMO-LUMO gap shows a decrease trend and average bond and coordinate number shows a decrease trend of even-number and odd-number clusters.(3)Even-numbered atom copper,silver and gold clusters are relatively more stable than the neighboring odd-sized ones and have a large HOMO-LUMO gap.(4)For the small copper and silver clusters,the structural from the plane[two-dimensional (2D)]to the three-dimensional(3D) geometry with n=6.However,the value of n=13 at which structural change of gold clusters.A sidestep of average bond and coordinate number are obtained at the structural from the 2D to the 3D.(5)The gold clusters show a strong sd hybridization orbit due to relativistic effects.