Nonlinear dynamics and surface diffusion of diatomic molecules

TL;DR

This paper investigates the complex nonlinear and chaotic behavior of diatomic molecules moving on surfaces, revealing how thermal diffusion deviates from simple models and can be significantly enhanced at low temperatures.

Contribution

It provides a detailed analysis of the nonlinear deterministic and thermal diffusive dynamics of dimers on periodic substrates, highlighting the impact of chaos and vibrational-translational coupling.

Findings

Dimer motion exhibits nonlinear and chaotic dynamics.

Thermal diffusion deviates from Arrhenius behavior due to vibrational-translational coupling.

Dimer diffusion can be much larger than single atoms at low temperatures.

Abstract

The motion of molecules on solid surfaces is of interest for technological applications, but it is also a theoretical challenge. We study the deterministic and thermal diffusive dynamics of a dimer moving on a periodic substrate. The deterministic motion of the dimer displays strongly nonlinear features and chaotic behavior. The dimer thermal diffusive dynamics deviates from simple Arrhenius behavior, due to the coupling between vibrational and translational degrees of freedom. In the low-temperature limit the dimer diffusion can become orders of magnitude larger than that of a single atom, as also found experimentally. The relation between chaotic deterministic dynamics and stochastic thermal diffusion is discussed.