Probing potential energy surface exploration strategies for complex systems

TL;DR

This paper investigates energy landscape exploration strategies for complex systems, demonstrating that traditional kinetic Monte Carlo methods are as effective as brute-force approaches and highlighting the limitations of the Bell-Evans-Polanyi principle.

Contribution

It compares different exploration strategies, confirms the Bell-Evans-Polanyi principle's limitations, and shows that standard kinetic Monte Carlo methods are efficient for complex energy landscapes.

Findings

BEP principle does not hold for complex systems.

KMC approach is as efficient as brute-force methods.

Crossing high-energy barriers is necessary for relaxation.

Abstract

The efficiency of minimum-energy configuration searching algorithms is closely linked to the energy landscape structure of complex systems. Here we characterize this structure by following the time evolution of two systems, vacancy aggregation in Fe and energy relaxation in ion-bombarded c-Si, using the kinetic Activation-Relaxation Technique (k-ART), an off-lattice kinetic Monte Carlo (KMC) method, and the well-known Bell-Evans-Polanyi (BEP) principle. We also compare the efficiency of two methods for handling non-diffusive flickering states -- an exact solution and a Tabu-like approach that blocks already visited states. Comparing these various simulations allow us to confirm that the BEP principle does not hold for complex system since forward and reverse energy barriers are completely uncorrelated. This means that following the lowest available energy barrier, even after removing the flickering states, leads to rapid trapping: relaxing complex systems requires crossing high-energy barriers in order to access new energy basins, in agreement with the recently proposed replenish-and-relax model [B\'eland et al., PRL 111, 105502 (2013)] This can be done by forcing the system through these barriers with Tabu-like methods. Interestingly, we find that following the fundamental kinetics of a system, though standard KMC approach, is at least as efficient as these brute-force methods while providing the correct kinetics information.