We present evidence for a fundamentally new mechanism impact-induced desorption, viz., core-hole Auger decay. thereby explain why observed thresholds electron-stimulated desorption (ESD) of positive ions (${\mathrm{O}}^{+}$, O${\mathrm{H}}^{+}$, and ${\mathrm{F}}^{+}$) from certain $d$-band metal oxides (Ti${\mathrm{O}}_{2}$, ${\mathrm{V}}_{2}$${\mathrm{O}}_{5}$, W${\mathrm{O}}_{3}$) correlate in energy with the ionization potential highest-lying atomic core levels. conclude that is many...

Notwithstanding half a dozen theoretical publications, well-converged density- functional calculations, whether based on local-density or generalized-gradient exchange-correlation potential, all-electron employing pseudopotentials, underestimate CO's preference for low-coordination binding sites Pt(111) and vicinals to it. For example, they imply that CO should prefer hollow- atop-site adsorption Pt(111), in apparent contradiction host of low-temperature experimental studies.

Lattices of Ir clusters have been grown by vapor phase deposition on graphene moir\'es Ir(111). The are highly ordered, and spatially thermally stable below 500 K. Their narrow size distribution is tunable from 4 to about 130 atoms. A model for cluster binding the presented based scanning tunneling microscopy density functional theory. proposed mechanism suggests that similar lattices might be materials other than Ir.

We describe the relation between observed behavior of photoemission energy distributions vs frequency, angle, etc., and quantum theory as recently set forth formally by Caroli et al. derive a Fermi's Golden-Rule formula for angle- energy-resolved photocurrent from an independent electron solid, show in detail approximations which render this equivalent to that familiar three-step model bulk photoemission. In terms formula, we account direct-transition band-structure regime generally at low...

Initial water deposition on the moderately reactive precious metal surface Ru(0001) has been thought to produce an ice-like bilayer. However, calculations from first principles show that wetting layer observed cannot be formed of undissociated molecules. An energetically favorable alternative, consistent with remarkable observation layer's oxygen atoms are nearly coplanar, is a half-dissociated monolayer wherein molecules and hydroxyl fragments hydrogen-bonded in hexagonal structure hydrogen...

Field-ion microscopy has been used to map the surface sites visited by an individual Pt adatom migrating at 175 K on Pt(001) plane and determine its activation energy for diffusion. Atomic displacements are found occur only in [100] or [010] directions. A surprisingly low of 0.47 eV is measured. These results consistent with a model which diffusion occurs adatom-substrate exchange mechanism. This mechanism predicted theoretically self-diffusion Al(001).

The barrier to self-diffusion on Al(001) by concerted displacement in a 〈100〉 or 〈010〉 direction is predicted be smaller than 1/3 that for ordinary Al-adatom hopping over bridges between fourfold hollows. transition state the motion corresponds an Al ad-dimer symmetrically located above surface site vacated one of dimer atoms. Covalent bonding this configuration favorable because each (trivalent) atoms bonds other, and two

A review of the electron-stimulated-desorption (ESD) literature shows that many features ESD are difficult to rationalize within model Menzel, Gomer, and Redhead can easily be interpreted using Auger decay model, which has recently been developed explain from transition-metal oxide surfaces. Specifically, helps charge state desorbing species, high-energy (\ensuremath{\sim} 30-40 eV) onset behavior is seen, differences in thresholds for positive neutral desorbates, cross-section...

For a long-wavelength electromagnetic wave of frequency $\ensuremath{\omega}$, incident on jellium-vacuum interface, the spatial dependence vector potential, $\stackrel{\ensuremath{\rightarrow}}{\mathrm{A}}(\stackrel{\ensuremath{\rightarrow}}{\mathrm{r}};\ensuremath{\omega})$, is evaluated in surface region. A simple integral equation derived which relates $\stackrel{\ensuremath{\rightarrow}}{\mathrm{A}}(\stackrel{\ensuremath{\rightarrow}}{\mathrm{r}};\ensuremath{\omega})$ to jellium...

Using low-energy electron microscopy (LEEM), we have measured the local concentration of mobile carbon adatoms from which graphene sheets form on a Ru(0001) surface, and simultaneously, growth rates individual islands. Graphene crystal Ru differs strikingly that two-dimensional metal islands metals: (i) C experience large energy barrier to attaching step edges, so adatom diffusion does not limit growth. (ii) The supersaturations needed for appreciable are comparable those required nucleate...

Graphene forms from a relatively dense, tightly bound C-adatom gas when elemental C is deposited on or segregates to the Ru(0001) surface. Nonlinearity of graphene growth rate with density suggests that proceeds by addition atom clusters edge. The generality this picture has now been studied use low-energy electron microscopy (LEEM) observe formation and Ir(111) surfaces are exposed ethylene. finding velocities nucleation rates Ru have precisely same dependence adatom concentration as for...

The authors report self-consistent linearized-augmented-plane-wave calculations of the electronic structure perburbations induced by a catalytic "poison," S, on Rh(001) surface, focusing particularly their distance dependence. S-induced charge density vanishes beyond immediately adjacent Rh atoms. However, Fermi-level states, which is not screened, and governs ability surface to respond presence other species, substantially reduced S even at non-adjacent sites.

Two contributions to the Green's-function formulation of electronic-structure calculations are described. We show that a seemingly minor change in definition relevant perturbed and unperturbed Green's functions eliminates several problems have hampered development formalism. Defining terms matrices, rather than differential operators, substantially simplifies description many systems, including displaced atoms, transition-metal impurities non-transition-metal hosts, chemisorbed atoms. In...

Enhancement of photoionization cross sections due to spatially varying photon fields at a metal surface has been observed in the normal-emission for state and Fermi level A1(100) energies between 9 eV 23 eV. The data Fermi-level photoexcitation are excellent agreement with theoretical results jellium. Below $\ensuremath{\hbar}{\ensuremath{\omega}}_{p}$, predominant contribution matrix element comes from fields, which provide momentum required photoexcitation.

Scanning tunneling topography of long-unexplained "square root 37" and 39" periodic wetting arrangements water molecules on Pt(111) reveals triangular depressions embedded in a hexagonal H2O-molecule lattice. Remarkably, the hexagons are rotated 30° relative to "classic bilayer" model water-metal adsorption. With support from density functional theory energetics image simulation, we assign clusters flat-lying molecules. 5- 7-member rings H2O separate these surrounding "H-down"

A first-principles, scattering-theory formalism is presented for the calculation of energy of, and forces on, a spatially localized group atoms in proximity to metallic crystalline surface. formula derived adsorption which rapidly convergent both with respect size matrix equations that must be solved number mesh points required numerical computation elements electron-electron potential. The force formula, following method Pulay, guarantees tangency calculated adsorption-energy surface if are...

We report a study of the valence band dispersion twisted bilayer graphene using angle-resolved photoemission spectroscopy and ab initio calculations. observe two noninteracting cones near Dirac crossing energy emergence van Hove singularities where overlap for large twist angles (>5°). Besides expected interaction between cones, minigaps appeared at Brillouin zone boundaries moiré superlattice formed by misorientation layers. attribute these to periodic potential induced moiré. These...

A self-consistent calculation of the electronic structure a thin Ti(0001) film leads to prediction band surface states coincident with Fermi level and extending few tenths an eV on either side it. The is performed in linear combination Gaussian orbitals basis. procedure by which evaluation Hamiltonian matrix reduced summing over three-center integrals as well method bases are selected thoroughly described. Observation predicted angle-resolved photoemission discussed, question how general...

Angle-resolved reflection inelastic electron scattering has been used to measure the dispersion of surface plasmon for thick films Na and K. The measured is negative at small momentum parallel as predicted by quantum-mechanical calculations dynamic response electrons an interacting gas. A simple physical picture presented explain origin surface-plasmon in metals.

Scanning tunneling microscopy (STM) images of water submonolayers on Pd(111) reveal quasiperiodic and isolated adclusters with internal structure that would ordinarily be ascribed to icelike puckered hexagonal units. However, density functional theory STM simulations contradict this conventional picture, showing instead the adlayers are composed mainly flat-lying molecules arranged in planar hexagons. A new rule for two dimensional (2D) growth is offered generates structures observed...

Exact microscopic formulas are derived for the surface optical properties of a jellium solid. The comparison these to those classically by McIntyre and Aspnes shows that $s$-polarized light, parametrization surface-reflectance data using classical theory is valid procedure, but $p$-polarized because short-wavelength fields induced in region, assumption local dielectric response invalid, thus prescription parametrizing reflectance unphysical.

Exact calculations of the linear coefficient surface-plasmon dispersion and damping $\ensuremath{\alpha}={\ensuremath{\alpha}}_{1}+i{\ensuremath{\alpha}}_{2}\ensuremath{\equiv}{\mathrm{lim}}_{q\ensuremath{\rightarrow}0}{q}^{\ensuremath{-}1}[\frac{{\ensuremath{\omega}}_{s}(q)}{{\ensuremath{\omega}}_{s}(0)}\ensuremath{-}1]$, using random-phase-approximation dynamical equation, for a jellium-vacuum interface characterized by smooth, finite, surface potential barrier are described in detail....