Poisoning of Hydrogen Dissociation at Pd (100) by Adsorbed Sulfur Studied by ab initio Quantum Dynamics and ab initio Molecular Dynamics

TL;DR

This study uses advanced quantum and molecular dynamics simulations to investigate how sulfur coverage on Pd (100) surfaces affects hydrogen dissociation, revealing complex dynamics and challenging previous simplified models.

Contribution

It provides a comprehensive ab initio analysis of hydrogen dissociation on sulfur-covered Pd (100), highlighting the importance of full degrees of freedom and complex PES effects.

Findings

Strongly corrugated potential energy surface influences dissociation

Tunneling and zero-point vibrations significantly affect dynamics

Traditional low-dimensional models may be invalid

Abstract

We report calculations of the dissociative adsorption of H_2 at Pd (100) covered with 1/4 monolayer of sulfur using quantum dynamics as well as molecular dynamics and taking all six degrees of freedom of the two H atoms fully into account. The ab initio potential-energy surface (PES) is found to be very strongly corrugated. In particular we discuss the influence of tunneling, zero-point vibrations, localization of the nuclei's wave function when narrow valleys of the PES are passed, steering of the approaching H_2 molecules towards low energy barrier configurations, and the time scales of the center of mass motion and the other degrees of freedom. Several ``established'' concepts, which were derived from low-dimensional dynamical studies, are shown to be not valid.