Memory effects in non-adiabatic molecular dynamics at metal surfaces

TL;DR

This paper investigates how memory effects influence non-adiabatic molecular dynamics at metal surfaces, demonstrating their importance for accurate energy conservation and dissipation modeling, especially in anharmonic systems.

Contribution

It introduces a method to incorporate memory effects into Langevin dynamics for non-adiabatic processes at metal surfaces, extending the approach to anharmonic potentials and proposing an ab-initio calculation scheme.

Findings

Memory effects are crucial for conserving ground state energy.

Langevin dynamics outperform master equations at high temperatures and large friction.

Memory effects reduce energy dissipation in desorption processes.

Abstract

We study the effect of temporal correlation in a Langevin equation describing non-adiabatic dynamics at metal surfaces. For a harmonic oscillator the Langevin equation preserves the quantum dynamics exactly and it is demonstrated that memory effects are needed in order to conserve the ground state energy of the oscillator. We then compare the result of Langevin dynamics in a harmonic potential with a perturbative master equation approach and show that the Langevin equation gives a better description in the non-perturbative range of high temperatures and large friction. Unlike the master equation, this approach is readily extended to anharmonic potentials. Using density functional theory we calculate representative Langevin trajectories for associative desorption of N$_2$ from Ru(0001) and find that memory effects lowers the dissipation of energy. Finally, we propose an ab-initio scheme to calculate the temporal correlation function and dynamical friction within density functional theory.