Modulating hydrogen diffusion on metal surfaces by nonadiabatic transitions

Nonadiabatic transitions may be used as a promising tool for dynamical control. However how it could be applied to and affect surface diffusion remains largely unexplored. Here a nonadiabatic model was proposed based on the classical mapping theory to introduce multistate couplings in addition to the bare surface diffusion. By performing nonadiabatic molecular dynamics simulation on a benchmark system of atomic hydrogen diffusion on the Cu (001) surface, it is demonstrated that nonadiabatic transitions could modulate diffusion dynamics in a robust way, i.e. either suppressing or promoting it. Depending on the design for the coupling regime in the nonadiabatic model, simulation results show that aside for the nonadiabatic damping effect, the diffusion constant of H atom could be enhanced by a factor of 2-6 in the temperature range of T = 500-600 K. The effect of nonadiabatic transitions may provide an explanation to the significant discrepancy between experimental measured diffusion constant and previous theoretical predictions. By highlighting the role of nonadiabatic effects, in particular under nonequilibrium conditions, this work sheds light on the development of new molecular control schemes for practical applications.