Advances in Modeling Phonon, Spin, Charge, and Chemical Dynamics

Adsorption of atomic and molecular hydrogen on surfaces is the gateway to many important chemical processes in nature. For realistic simulations of adsorption of hydrogen atoms or molecules at metal surfaces, or light-driven desorption, accurate couplings between the gaseous particles and the substrate’s electronic states are essential. However, their acquisition and utilisation for molecular dynamics is not straightforward if one wishes to account for the spectral properties of the substrate.

Here, we present a pragmatic protocol based on the projector diabatisation operator (POD) approach that allows for the acquisition of electronic couplings between adsorbate and metallic substrates. Since the POD approach relies on partitioning the states of the total system into an adsorbate subset and a substrate subset, it has primarily applied to weakly interacting systems, whilst its aplicability to strongly interacting systems has been questioned. Here, we will present a strategy to overcome this issue and apply our workflow to strongly interacting systems, i.e., atomic hydrogen adsorbed on metal surfaces. We show that we can verify the validity of this projection by reconstructing the projected density of states of the adsorbate, and extracting electron tunnelling rates. We further connect these electronic couplings to vibrational relaxation rates due to electron-hole pair (ehp) excitation. This allows for comparing our acquired results to reflective IR measurements, and pump-probe experiments. Finally, we outline how this approach allows for the construction of Newns-Anderson Hamiltonians, the standard model in gas-surface dynamics to describe the interaction of a single adsorbate state with a continuum of metal states.