Molecular dynamics simulations for xenon adsorption on Pt(111): dynamical differences in the effects produced by the Barker-Rettner and Morse potentials

SURFACE SCIENCE

卷:391

Article

Weaver, JF ; Stinnett, JA ; Madix, RJ

关键词: adsorption kinetics;    atom-solid interactions;    computer simulations;    molecular dynamics;    platinum;   

DOI  :  10.1016/S0039-6028(97)00478-0

来源: Elsevier

【 摘 要 】

In order to gain a better insight into the effects of gas-surface potential functions and on observable quantities related to adsorption, xenon trapping on cold Pt(111) was simulated using classical three-dimensional stochastic trajectory calculations with a pairwise additive Morse potential and a potential developed by Barker and Rettner [J. Chem. Phys. 97 (1992) 5844]. Both potentials predict the same dependence of the initial trapping probability on the translational energy and angle of incidence of the colliding xenon atoms, but only the Barker-Rettner potential gives agreement with the observed in-plane scattered distributions, thus providing a basis for distinguishing the potentials. The features of the potentials that determine the differences in collisional dynamics are the potential corrugation and the steepness of the repulsive wall. Corrugation causes substantial scrambling between the components of incident gas-atom parallel and normal momentum, whereas the impulsiveness of the collisions determines the efficiency of energy transfer between the gas and surface. Long collision times computed for the softer Morse potential result in secondary surface recoil effects which cause scattering xenon atoms to gain normal momentum from the vibrationally excited surface; these effects are absent in the impulsive Barker-Rettner potential. These differences in the microscopic dynamics predicted by the potentials strongly effect the computed scattering distributions, but are compensatory in predicting the initial trapping probabilities. The Barker-Rettner potential behaves much like traditional hard cube models, whereas the Morse potential predicts that the efficacious dissipation of incident parallel momentum to the surface facilitates trapping at glancing incidence. (C) 1997 Elsevier Science B.V.

【 授权许可】

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