Enigmatic HCl + Au(111) Reaction: A Puzzle for Theory and Experiment

Abstract

an accurate potential energy surface incorporating the six adsorbate degrees of freedom of HCl on Au(111) by using the neural network approach. In our molecular dynamics simulations, we model the experimental beam conditions to study the influence of the rovibrational state population distribution of HCl in the molecular beam on reaction. Likewise, molecular dynamics with electronic friction calculations based on the parameterfree local density friction approximation in the independent atom approximation (LDFA-IAA) are performed to get first insights into how electron hole pair excitation might affect the reactivity of HCl. Although satisfying agreement with the experiment could not yet be achieved by our simulations, we find that i) RPBE yields larger reaction barriers than PBE and lower computed reaction probabilities, improving the agreement with experiment, ii) the reactivity strongly depends on the rovibrational state population, iii) surface atom motion and electronically non-adiabatic effects modeled with the efficient to use but approximate LDFA influence the reaction only modestly, and iv) a moderate amount of charge is transferred from the surface to the dissociating molecule at the transition state. We suggest that the reported experimental reaction probabilities could be too low by a factor of about 2-3, due to potential problems with calibrating coverage of Au by Cl using an ill-defined external standard in the form of Auger peak ratios. However, taking this factor into account would not yet resolve the discrepancy between the theoretical reaction probabilities presented here and the experimental sticking probabilities.

Energy dissipation at metal surfaces

“…Indeed, for the aforementioned CH 4 dissociation (where both effects are known to be important [76]) Kroes and coworkers predicted satisfying, semi-quantitative agreement to experimental reaction probabilities [84]. In the meantime, similar results have also been reached for H 2 [37,85,86], N 2 [87,88], O 2 [89], and CO 2 [78] adsorbates, overall showing AIMD simulations to provide a reasonable account of surface temperature effects. With reaction probabilities as the target observable, the effective advantage of the detailed AIMD account of adsorbate-surface energy transfer-over corresponding, numerically more attractive SO/GLO modelsultimately depends on the importance of thermal fluctuations (assuming of course the validity of the single-phonon approximation).…”

Vibrational Excitation of H2 Scattering from Cu(111): Effects of Surface Temperature and of Allowing Energy Exchange with the Surface

“…Depending on the simulation, either the incidence direction was normal to the surface or the incidence angles were taken equal to the experimental values (see below). A Monte Carlo integration was performed over randomly selected impact points on the surface and initial orientation angles and directions of rotational velocities, in accordance with the initial value of j and the initial magnetic rotational quantum number m j (the projection of j on the surface normal) as described in, for instance, ref (49). In the AIMDEF calculations, a uniform sampling of m j was performed by running equal numbers of trajectories for − j ≤ m j ≤ j .…”

Semi-classical generalized Langevin equation for equilibrium and nonequilibrium molecular dynamics simulation

“…Although the studied system could be made from different kinds of DoF [9], the most widely studied one is nuclear or atomic or phononic DoF under the influence of thermal baths [10][11][12][13][14][15][16][17][18]. Interesting applications include the study of nuclear quantum effects [17][18][19][20][21][22][23][24][25][26], heat transport between two different thermal baths [12][13][14][15][16][27][28][29][30][31][32][33][34][35][36][37], scattering of single molecule on surfaces [38][39][40][41][42][43][44][45][46][47][48][49][50]…”