arXiv subjects

S. Holloway

Publications and source records attributed to S. Holloway.

4 recordsLinked to original sources

arXiv2009

Electron-hole pair creation by atoms incident on a metal surface

Electron-hole pair creation by an adsorbate incident on a metal surface is described using \textit{ab initio} methods. The approach starts with standard first principles electronic structure theory, and proceeds to combine classical, quantum oscillator and time dependent density functional methods to provide a consistent description of the non-adiabatic energy transfer from adsorbate to substrate. Of particular interest is the conservation of the total energy at each level of approximation, and the importance of a spin transition as a function of the adsorbate/surface separation. Results are presented and discussed for H and D atoms incident on the Cu(111) surface.

cond-mat.mtrl-sci↗

arXiv2009

Energy loss of atoms at metal surfaces due to electron-hole pair excitations: First-principles theory of "chemicurrents"

A method is presented for calculating electron-hole pair excitation due to an incident atom or molecule interacting with a metal surface. Energy loss is described using an \textit{ab initio} approach that obtains a position-dependent friction coefficient for an adsorbate moving near a metal surface from a total energy pseudopotential calculation. A semi-classical forced oscillator model is constructed, using the same friction coefficient description of the energy loss, to describe excitation of the electron gas due to the incident molecule. This approach is applied to H and D atoms incident on a Cu(111) surface, and we obtain theoretical estimates of the `chemicurrents' measured by Nienhaus et al [Phys. Rev. Lett. \textbf{82}, 446 (1999)] for these atoms incident on the surface of a Schottky diode.

cond-mat.mtrl-sci↗

arXiv2008

Newns-Anderson model of chemicurrents in H/Cu and H/Ag

The excitation of the electronic system induced by the adsorption of a hydrogen atom on the (111) surfaces of copper and silver is investigated using the time-dependent, mean-field Newns-Anderson model. Parameters for the model are obtained by fitting to density functional theory calculations, allowing the charge and energy transfer between adsorbate and surface to be calculated, together with the spectrum of electronic excitations. These results are used to make direct comparisons with experimental measurements of chemicurrents, yielding good agreement for both the magnitude of the current and the ratio of the currents for H and D adsorption.

cond-mat.mtrl-sci↗

arXiv2006

Spectrum of electronic excitations due to the adsorption of atoms on metal surfaces

The time-dependent, mean-field Newns-Anderson model for a spin-polarised adsorbate approaching a metallic surface is solved in the wide-band limit. Equations for the time-evolution of the electronic structure of the adsorbate-metal system are derived and the spectrum of electronic excitations is found. The behaviour of the model is demonstrated for a set of physically reasonable parameters.

cond-mat.mtrl-sci↗