Memory effects in nonadiabatic molecular dynamics at metal surfaces

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 N2 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.

Ab initiotensorial electronic friction for molecules on metal surfaces: Nonadiabatic vibrational relaxation

“…Considering approximate friction methods, such as the LDFA, [48][49][50] this approach may serve as a reference that guides the improvement of LDFA beyond the local density limit, for example towards incorporation of semi-local contributions that correlate with the electron density gradient. Future work would be needed to study the applicability and usefulness of our approach in nonadiabatic dynamics on surfaces and its potential extensions towards dynamics beyond the weak coupling limit, 46 dynamics including explicit memory effects, 127 and the efficient incorporation of excited state screening. 93,94…”

Hot electron effects during reactive scattering of H2 from Ag(111): assessing the sensitivity to initial conditions, coupling magnitude, and electronic temperature

“…It has recently been pointed out that such broadening introduces contributions that are not rigorously contained in a zero-frequency 1 st order approximation 32 and leads to relaxation rates that depend on the choice of broadening. This dependence remains a weak spot in this theory and has been discussed in detail in our previous work, 31 yet, in lieu of a feasible non-Markovian MDEF approach, 39 this pragmatic choice delivers a meaningful way to calculate relaxation rates beyond the LDFA 24,31,40,41 that correctly capture the directional and electronic structure dependence of the friction tensor. All elements of the friction tensor are calculated as a function of the adsorbate atom position using the all-electron, local atomic orbital code FHI-aims 42 and the Perdew-Burke-Ernzerhof (PBE) functional.…”

Constrained Density Functional Theory

“…This reaction continues to attract significant interest in surface science. More recent theoretical studies have employed nonadiabatic surface-hopping MD simulations and have considered the roles of self-interaction error and memory effects on adsorption at metal surfaces. In these studies, CDFT provides a convenient way to capture nonadiabaticity by forcing molecules to preserve their proper spin states as they begin to interact.…”