A six-dimensional potential energy surface for Ru(0001)(2×2):CO

We present a new global ground state potential energy surface (PES) for carbon monoxide at a coverage of 1/4, on a rigid Ru(0001) surface [Ru(0001)(2×2):CO]. All six adsorbate degrees of freedom are considered. For constructing the PES, we make use of more than 90 000 points calculated with periodic density functional theory using the RPBE exchange-correlation functional and an empirical van der Waals correction. These points are used for interpolation, utilizing a symmetry-adapted corrugation reducing procedure (CRP). Three different interpolation schemes with increasing accuracy have been realized, giving rise to three flavours of the CRP PES. The CRP PES yields in agreement with the DFT reference and experiments, the atop position of CO to be the most stable adsorption geometry, for the most accurate interpolation with an adsorption energy of 1.69 eV. The CRP PES shows that diffusion parallel to the surface is hindered by a barrier of 430 meV, and that dissociation is facilitated but still activated. As a first “real” application and further test of the new potential, the six-dimensional vibrational Schrödinger equation is solved variationally to arrive at fully coupled, anharmonic frequencies and vibrational wavefunctions for the vibrating, adsorbed CO molecule. Good agreement with experiment is found also here. Being analytical, the new PES opens an efficient way towards multidimensional dynamics

Photochemistry and spectroscopy of molecules at surfaces: Insights from ab initio molecular dynamics

Resumen del trabajo presentado al 2nd CECAM Workshop: "Challenges in reaction dynamics of gas-­surface interactions and methodological advances in dissipative and non­adiabatic processes", celebrado en Toulouse (France) del 27 al 30 de septiembre de 2021.Peer reviewe

Strong anisotropic interaction controls unusual sticking and scattering of CO at Ru(0001)

Complete sticking at low incidence energies and broad angular scattering distributions at higher energies are often observed in molecular beam experiments on gas-surface systems which feature a deep chemisorption well and lack early reaction barriers. Although CO binds strongly on Ru(0001), scattering is characterized by rather narrow angular distributions and sticking is incomplete even at low incidence energies. We perform molecular dynamics simulations, accounting for phononic (and electronic) energy loss channels, on a potential energy surface based on first-principles electronic structure calculations that reproduce the molecular beam experiments. We demonstrate that the mentioned unusual behavior is a consequence of a very strong rotational anisotropy in the molecule-surface interaction potential. Beyond the interpretation of scattering phenomena, we also discuss implications of our results for the recently proposed role of a precursor state for the desorption and scattering of CO from ruthenium.I. L. and J. I. J. acknowledge financial support by the Gobierno Vasco-UPV/EHU Project IT756-13, and the Spanish Ministerio de Economía y Competitividad (Grants No. FIS2013-48286-C2-2-P and No. FIS2016-76471-P). P. S. acknowledges support by Deutsche Forschungsgemeinschaft through Project No. Sa 547/8. G. F. thanks the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO-CW) for financial support through a TOP grant.Peer Reviewe

Reactive and nonreactive scattering of HCl from Au(111): An Ab initio molecular dynamics study

The HCl + Au(111) system has recently become a benchmark for highly activated dissociative chemisorption, which presumably is strongly affected by electron–hole pair excitation. Previous dynamics calculations, which were based on density functional theory at the generalized gradient approximation level (GGA-DFT) for the molecule–surface interaction, have all overestimated measured reaction probabilities by at least an order of magnitude. Here, we perform ab initio molecular dynamics (AIMD) and AIMD with electronic friction (AIMDEF) calculations employing a density functional that includes the attractive van der Waals interaction. Our calculations model the simultaneous and possibly synergistic effects of surface temperature, surface atom motion, electron–hole pair excitation, the molecular beam conditions of the experiments, and the van der Waals interaction on the reactivity. We find that reaction probabilities computed with AIMDEF and the SRP32-vdW functional still overestimate the measured reaction probabilities, by a factor 18 for the highest incidence energy at which measurements were performed (≈2.5 eV). Even granting that the experiment could have underestimated the sticking probability by about a factor three, this still translates into a considerable overestimation of the reactivity by the current theory. Likewise, scaled transition probabilities for vibrational excitation from ν = 1, j = 1 to ν = 2 are overestimated by the AIMDEF theory, by factors 3–8 depending on the initial conditions modeled. Energy losses to the surface and translational energy losses are, however, in good agreement with experimental values.This work was supported financially by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO-CW) through a TOP grant and by the European Research Council through an ERC advanced grant (no. 338580), and with computer time granted by NWO-EW. B.J. acknowledges the support by National Natural Science Foundation of China (91645202, 21722306, and 21573203) and Fundamental Research Funds for the Central Universities (WK2060190082 and WK2340000078). H.G. thanks the U.S. National Science Foundation (CHE-1462109) for generous support. J.I.J. and M.A. acknowledge the Spanish Ministerio de Economia, Industria y Competitividad grant no. FIS2016-76471-P.Peer reviewe