Scattering of NO(ν = 3) from Au(111): a stochastic dissipative quantum dynamical perspective

In this work, we present a theoretical study of the scattering dynamics of NO(ν = 3) from an ideal unreconstructed Au(111) surface. The simulations are performed in reduced dimensions at the three high-symmetry sites employing our recent modification to the stochastic wave packet approach for diatomic-metal scattering [J. Chem. Phys., 2019, 150, 184105]. Energy exchange between molecular vibrational degrees of freedom and the electron-hole pairs (EHP) of the metal is accounted for by quantized stochastic jump operators, with associated rates obtained from a microscopic model based on Fermi's golden rule. The simulations are found to reproduce the experimentally observed trend of enhanced vibrational relaxation probabilities with increasing initial translational energy. Molecular dynamics simulations with electronic friction (MDEF) in the independent atom approximation were performed to compare classical and quantum dynamical descriptions of that system. Significant differences between these two descriptions were found indicating that intermode coupling must be described accurately by using a good potential energy surface, and pointing out at the potentially important influence of a quantized description of energy relaxation in describing the scattering of NO from Au(111).

Stochastic wave packet approach to nonadiabatic scattering of diatomic molecules from metals

In this contribution, we present a quantum dynamical approach to study inelastic scattering of diatomic molecules from metal surfaces at normal incidence. The dissipative dynamics obeys a stochastic Schrödinger equation describing the time-evolution of the system as a piecewise deterministic process. Energy exchange between the molecular vibrational degrees of freedom and the metal electrons is represented using operators in tensor product form, which are coupled via anharmonic transition rates calculated from first-order perturbation theory. Full dimensional observables are obtained by averaging over simulations in 4D-including the internal stretch, the distance to the surface, and the orientation angles-at different surface sites. The method is applied to the state-resolved scattering of vibrationally excited NO from Au(111), revealing important channels for quantized energy relaxation.

Intermode Coupling Drives the Irreversible Tautomerization in Porphycene on Copper(111) Induced by Scanning Tunnelling Microscopy

In this contribution, we develop a nonadiabatic theory that explains, from first-principles, the recently reported irreversible trans → cis tautomerization of porphycene on Cu(111) induced by a scanning tunnelling microscope at finite bias. The inelastic contribution to the STM current is found to excite a large number of skeletal vibrational modes of the molecule, thereby inducing a deformation of the potential energy landscape along the hydrogen transfer coordinate. Above a threshold bias, the stability of the tautomers is reversed, which indirectly drives the reaction via intermode coupling. The proposed potential deformation term accounts effectively for the excitation of all internal vibrational modes without increasing the dimensionality of the problem. The model yields information about reaction rates, explains the reaction irreversibility at low temperatures, and accounts for the presence of resonant processes.

Hydrogen diffusion into the subsurfaces of model metal catalysts from first principles

We present in detail the diffusion pathways of hydrogen on seven different open and closed model catalyst surfaces from first principles calculations.