Communication: Hot-atom abstraction dynamics of hydrogen from tungsten surfaces: The role of surface structure

Abstract

Adiabatic and non-adiabatic quasiclassical molecular dynamics simulations are performed to investigate the role of the crystal face on hot-atom abstraction of H adsorbates by H scattering from covered W(100) and W(110). On both cases, hyperthermal diffusion is strongly affected by the energy dissipated into electron-hole pair excitations. As a result, the hot-atom abstraction is highly reduced in favor of adsorption at low incidence energy and low coverages, i.e., when the mean free path of the hyperthermal H is typically larger. Qualitatively, this reduction is rather similar on both surfaces, despite at such initial conditions, the abstraction process involves more subsurface penetration on W(100) than on W(110).

Ab initio molecular dynamics study of the Eley-Rideal reaction of H + Cl–Au(111) → HCl + Au(111): Impact of energy dissipation to surface phonons and electron-hole pairs

“…[44][45][46] It is also similar to the large EHP-induced dissipation on the H + H* recombination on tungsten surfaces. 37,38 In that case, however, the energy loss was predicted to be sufficient to reduce the reactivity substantially because the ER exothermicity of the H + H* → H 2 reaction is significantly smaller (1.5 eV) than in the current case (2.68 eV), and the corresponding LH reaction is strongly endothermic (∆E = 1.5 eV). Thus, slower H atoms may not be able to overcome the endothermicity and thus get trapped.…”

“…[44][45][46] More recently, it was predicted that EHP-induced dissipation can greatly reduce the H + H* HA recombination reactivity on tungsten surfaces. 37,38 Thus, it is imperative to include both dissipation channels in dynamical studies, particularly, if they involve light atoms or adsorbates. 36,47 Many earlier theoretical models for ER/HA dynamics have relied on analytical PESs assuming a rigid surface.…”

“…In more recent studies, energy exchange with surface phonons has been approximated either with simple surface oscillators 24,29 or a generalized Langevin oscillator model. 32,33,36 On the other hand, the effects of EHPs have been explored [36][37][38][39] using the local density friction approximation (LDFA), 48 which expresses the non-adiabatic interaction with the surface EHPs as a friction term in the dynamical equation. 49 For the current system, the importance of EHPs has been suggested previously, but only a semi-empirical correction was considered.…”

Translational Inelasticity of Hydrogen Atoms Scattering off Hydrogen-Covered W(110) Surfaces

“…The random force term has often been neglected when surface electron temperature is not high, as in the works rationalizing the relaxation of H hot-atoms on bare metallic surface, [28][29][30] or diatom recombination. 18,19,31 However, this term is crucial when elementary surface processes are triggered by intense laser pulses causing electrons to be heated up to a few thousands of Kelvin. 27,[32][33][34][35][36][37][38] Recently, this term has been also shown to sensibly alter the shape of specular energy loss spectra of hydrogen scattering from clean metal surfaces 39 even at ambient temperatures.…”

“…Besides, studies on H 2 diatom recombination by collision of H atoms on H-covered Tungsten surfaces have also highlighted the major influence of ehp excitations for slowing down and stopping Hot-Atoms initially diffusing at hyperthermal velocities on surfaces. 18,19 2 To the best of our knowledge, the translation energy loss of H atom scattering off surfaces have only been measured and rationalized for clean metal surfaces. However, as H adsorption on metal is a very efficient process, the question which then arises is : how is the energy transfer to the surface affected when surface gets populated with adsorbates?…”