Structural relaxation in atomic clusters: Master equation dynamics

TL;DR

This paper investigates how the energy landscape influences the relaxation dynamics of atomic clusters using a master equation approach, comparing single and double funnel landscapes and exploring the effects of potential range.

Contribution

It introduces a master equation framework to analyze relaxation in atomic clusters, incorporating anharmonic effects and limited landscape data, with implications for proteins and glasses.

Findings

Decreasing potential range hinders relaxation to the global minimum.

Interfunnel rate constants can be extracted from the master equation.

Conditions for applying the master equation to limited data are identified.

Abstract

The role of the potential energy landscape in determining the relaxation dynamics of model clusters is studied using a master equation. Two types of energy landscape are examined: a single funnel, as exemplified by 13-atom Morse clusters, and the double funnel landscape of the 38-atom Lennard-Jones cluster. Interwell rate constants are calculated using Rice-Ramsperger-Kassel-Marcus theory within the harmonic approximation, but anharmonic model partition functions are also considered. Decreasing the range of the potential in the Morse clusters is shown to hinder relaxation towards the global minimum, and this effect is related to the concomitant changes in the energy landscape. The relaxation modes that emerge from the master equation are interpreted and analysed to extract interfunnel rate constants for the Lennard-Jones cluster. Since this system is too large for a complete characterization of the energy landscape, the conditions under which the master equation can be applied to a limited database are explored. Connections are made to relaxation processes in proteins and structural glasses.