Activated sampling in complex materials at finite temperature: the properly-obeying-probability activation-relaxation technique

TL;DR

The paper introduces POP-ART, an extension of ART that correctly samples thermodynamic ensembles in complex systems at finite temperature, improving efficiency over MD in certain diffusion processes.

Contribution

It presents POP-ART, a new method that obeys detailed balance and accurately samples thermodynamic ensembles, addressing limitations of previous ART methods.

Findings

POP-ART recovers proper thermodynamic weights.

POP-ART is faster than MD below 700 K for vacancy diffusion.

Method validated on crystalline silicon defect models.

Abstract

While the dynamics of many complex systems is dominated by activated events, there are very few simulation methods that take advantage of this fact. Most of these procedures are restricted to relatively simple systems or, as with the activation-relaxation technique (ART), sample the conformation space efficiently at the cost of a correct thermodynamical description. We present here an extension of ART, the properly-obeying-probability ART (POP-ART), that obeys detailed balance and samples correctly the thermodynamic ensemble. Testing POP-ART on two model systems, a vacancy and an interstitial in crystalline silicon, we show that this method recovers the proper thermodynamical weights associated with the various accessible states and is significantly faster than MD in the diffusion of a vacancy below 700 K.