Competition between Electron and Phonon Excitations in the Dynamics of Nitrogen Atoms and Molecules at Metal Surfaces

L. MARTIN-GONDRE; M. ALDUCIN; G.A. BOCAN; K. R. GEETHALAKSHMI; J.I. JUARISTI; R. DÍEZ MUIÑO

Edinburgo

Congreso; 29th European Conference on Surface Science; 2012

Institute of Physics (IOP)

<!-- @page { margin: 0.79in } P { margin-bottom: 0.08in; direction: ltr; color: #000000; widows: 2; orphans: 2 } P.western { font-family: "Times", serif; font-size: 11pt; so-language: en-GB } P.cjk { font-size: 11pt } --> 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 [1]. The model is applied to study energy dissipation in the scattering and adsorption of nitrogen atoms and molecules in different metal surfaces. In non-reactive scattering processes, 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. In atomic adsorption, the two dissipative channels play a different role during the dynamics: phonons are responsible for determining the adsorption probability but electronic excitations are relevant at a later stage to fix the atoms to the adsorption positions. We also discuss the role of exchange-correlation in the theoretical description of the adiabatic interaction when using density functional theory [2]. We show that the dynamics of scattering processes at surfaces can be used as a valuable tool to test methodological advances in this respect. <!-- @page { margin: 0.79in } P { margin-bottom: 0.08in; direction: ltr; color: #000000; widows: 2; orphans: 2 } P.western { font-family: "Times", serif; font-size: 11pt; so-language: en-GB } P.cjk { font-size: 11pt } --> References [1] L. Martin-Gondre, M. Alducin, G. A. Bocan, R. Díez Muiño, and J. I. Juaristi, 2012 Phys. Rev. Lett.108 096101. [2] K. R. Geethalakshmi, J. I. Juaristi, R. Díez Muiño, and M. Alducin, 2011, Phys. Chem. Chem. Phys.13, 4357.