0000000000255898
AUTHOR
Uzi Landman
Trianionic gold clusters
Using Penning-trap experiments and a shell-correction method incorporating ellipsoidal shape deformations, we investigate the formation and stability patterns of trianionic gold clusters. Theory and ex- periment are in remarkable agreement concerning appearance sizes and electronic shell eects. In contrast to multiply cationic clusters, decay of the trianionic gold clusters occurs primarily via electron autodetach- ment and tunneling through a Coulomb barrier, rather than via ssion. PACS. 36.40.Wa Charged clusters { 36.40.Qv Stability and fragmentation of clusters { 36.40.Cg Electronic and magnetic properties of clusters
Multiply charged metal cluster anions
Formation, stability patterns, and decay channels of silver dianionic and gold trianionic clusters are investigated with Penning-trap experiments and a shell-correction method including shape deformations. The theoretical predictions pertaining to the appearance sizes and electronic shell effects are in remarkable agreement with the experiments. Decay of the multiply anionic clusters occurs predominantly by electron tunneling through a Coulomb barrier, rather than via fission, leading to appearance sizes unrelated to those of multiply cationic clusters.
Aluminum cluster anions: Photoelectron spectroscopy andab initiosimulations
Atomic structures and geometries, electronic structure, and temperature-dependent photoelectron spectra of ${\mathrm{Al}}_{N}^{\ensuremath{-}} (N=19\ensuremath{-}102)$ clusters are studied both theoretically via ab initio local-density-functional simulations, and experimentally with high-resolution measurements. The use of a theoretically well-defined energy shift in conjunction with a generalized Koopmans' theorem enables direct comparisons between the calculated density of states and the experimental photoelectron spectrum. Such comparisons, using photoelectron spectra calculated for various relaxed cluster geometries, enables a determination of the optimal structures of the clusters. The…
Molecular Dynamics Study of Disordering and Premelting of the Pb(110) Surface
Molecular dynamics simulations incorporating a many-body (glue) potential have been used to investigate the atomic structure and dynamics of the Pb(110) surface in the range from room temperature up to the bulk melting point. The Pb (110) surface starts to disorder approximately at 360 K via the generation of vacancies and the formation of an adlayer. At about 520 K we observe the onset of a quasiliquid region at the surface, which exhibits liquid-like energetic, structural and surface properties. The disordering is enhanced in the direction parallel to the close-packed rows. While losing long range order, the two outermost quasiliquid layers retain a considerable degree of short range orde…
Oxidation of small gas phase Pd clusters: A density functional study
The adsorption sites of O2 on neutral PdN clusters (N = 1–4) were studied using spin density functional theory. Only for Pd1O2 molecular adsorption is found to be favorable. For Pd2–4O2 dissociative adsorption with the oxygen sitting on Pd bridge sites is preferred. Most Pd clusters remain in the same high spin states found for pure gas phase Pd clusters. Only the ground state of Pd4O2 increase its spin from a triplet to a quintet state. For molecular adsorption the O–O bond gets activated to a superoxo-like state.
Photoelectron spectra of aluminum cluster anions: Temperature effects and ab initio simulations
Photoelectron (PES) spectra from aluminum cluster anions (from 12 to 15 atoms) at various temperature regimes, were studied using ab-initio molecular dynamics simulations and experimentally. The calculated PES spectra, obtained via shifting of the simulated electronic densities of states by the self-consistently determined values of the asymptotic exchange-correlation potential, agree well with the measured ones, allowing reliable structural assignments and theoretical estimation of the clusters' temperatures.
Metallization of the Na 14 Cl 13 Cluster
The structure and energetics of multiple-excess-electron alkali halide clusters Na14Cl14-n, (1 ≤ n ≤ 6) is studied by ab initio calculations using norm-conserving pseudopotentials and local-spin-density-functional theory. Analysis of various electronic properties (Kohn-Sham one-electron eigenvalue spectra, ionization potentials, participation ratios of Kohn-Sham orbitals), as well as multiple F-center formation energies, suggests that these clusters can be characterized as Nan(NaCl)14-n having a "phase-separated" metallic part NaI. The Na14Cl9 (or Na14Cl9+) cluster exhibits a face (surface) segregated metallic Na5 (Na5+) overlayer, the stability of which is demonstrated by a molecular-dynam…
Size-Dependent Structural Evolution and Chemical Reactivity of Gold Clusters
Ground-state structures and other experimentally relevant isomers of Au(15) (-) to Au(24) (-) clusters are determined through joint first-principles density functional theory and photoelectron spectroscopy measurements. Subsequent calculations of molecular O(2) adsorption to the optimal cluster structures reveal a size-dependent reactivity pattern that agrees well with earlier experiments. A detailed analysis of the underlying electronic structure shows that the chemical reactivity of the gold cluster anions can be elucidated in terms of a partial-jellium picture, where delocalized electrons occupying electronic shells move over the ionic skeleton, whose geometric structure is strongly infl…