Nonlinear dynamics of dimers on periodic substrates

TL;DR

This paper investigates the complex nonlinear dynamics of dimers on periodic substrates, revealing various motion regimes, resonance phenomena, and conditions for dissociation, relevant for understanding surface molecular behavior.

Contribution

It provides a detailed analysis of the nonlinear dynamical regimes of dimers on periodic surfaces, including chaos and dissociation mechanisms, using Lyapunov exponents and spectral analysis.

Findings

Identification of oscillatory, quasi-diffusive, and drift regimes.

Chaotic behavior occurs over a broad velocity range for weakly bound dimers.

Dimer dissociation can be triggered by parametric excitation of internal vibrations.

Abstract

We study the dynamics of a dimer moving on a periodic one-dimensional substrate as a function of the initial kinetic energy at zero temperature. The aim is to describe, in a simplified picture, the microscopic dynamics of diatomic molecules on periodic surfaces, which is of importance for thin film formation and crystal growth. We find a complex behaviour, characterized by a variety of dynamical regimes, namely oscillatory, ``quasi-diffusive'' (chaotic) and drift motion. Parametrically resonant excitations of internal vibrations can be induced both by oscillatory and drift motion of the centre of mass. For weakly bound dimers a chaotic regime is found for a whole range of velocities between two non-chaotic phases at low and high kinetic energy. The chaotic features have been monitored by studying the Lyapunov exponents and the power spectra. Moreover, for a short-range interaction, the dimer can dissociate due to the parametric excitation of the internal motion.