Competition between Electron and Phonon Excitations in the Scattering of Nitrogen Atoms and Molecules off Tungsten and Silver Metal Surfaces

Abstract

We investigate the role played by electron-hole pair and phonon excitations in the interaction of reactive gas molecules and atoms with metal surfaces. We present a theoretical framework that allows us to evaluate within a full-dimensional dynamics the combined contribution of both excitation mechanisms while the gas particle-surface interaction is described by an ab initio potential energy surface. The model is applied to study energy dissipation in the scattering of N(2) on W(110) and N on Ag(111). Our results show that phonon excitation is the dominant energy loss channel, whereas electron-hole pair excitations represent a minor contribution. We substantiate that, even when the energy dissipated is quantitatively significant, important aspects of the scattering dynamics are well captured by the adiabatic approximation.

Scattering of Nitrogen Atoms off Ag(111) Surfaces: A Theoretical Study

“…Further details about this combination are given elsewhere. 8,30 In order to assess the effect of the effusive beam on the experimental results, 36 we start by using a monoenergetic beam of E i = 4.3 eV. This simulation shows that reflection is the dominant process.…”

“…8 In the experimental studies, 36 A detailed analysis of the trajectories can be done by performing a decomposition of the angular distribution as shown in Figure 7 for Θ i = 60 • . This decomposition is based on the minimum distance to the surface Z re f reached by the N atoms.…”

“…There are recent examples in the literature where the interplay of multidimensional and non-adiabatic effects has been assessed using these methodologies. [6][7][8][9][10][11][12] In the present paper, we have used these techniques to obtain an accurate theoretical description of the N-Ag(111) interaction by means of a full three-dimensional adiabatic PES, constructed from ab-initio data and an elaborate interpolation method. 13 The two types of aforementioned energy loss channels are accounted for later, within classical MD simulations.…”

“…It has also been shown that an adiabatic model suffices to account for the angular distributions of the final kinetic energies of the reflected N atoms, albeit energy dissipation channels are required to obtain a good match with the experimental values. 8 As in N adsorption, dissipation into lattice phonons also comes through as the dominant energy loss mechanism in N reflection.…”

Modeling Heat Dissipation at the Nanoscale: An Embedding Approach for Chemical Reaction Dynamics on Metal Surfaces

“…[2] Complementing this with a quantitative account of substrate phonons has been cited one of the major conceptual problems in contemporary gas-surface dynamical modeling. [10][11][12] Current state-ofthe-art ab initio molecular dynamics (AIMD) simulations allow for such substrate mobility, but only within computationally tractable supercells and slab models comprising a few surface lattice constants and layers. In contrast, a simple estimate of the phonon propagation distance in metals according to the speed of sound yields tens of lattice constants per pico second in each direction.…”