Generalized valence bond molecular dynamics at constant temperature

The Nosé–Hoover chain thermostat of Martyna, Klein and Tuckerman has been adapted to work with our generalized valence bond ab initio molecular dynamics (AIMD) method, allowing us to perform AIMD in the canonical ensemble (constant number of particles temperature and volume). The canonical ensemble is ideal for simulated annealing which can be used to find global potential energy minima. The efficacy of constant-temperature-based AIMD simulated annealing is demonstrated for a Si₆ cluster and is compared with that of a non-constant-temperature-based method. It is found that in comparison with the velocity-scaling approach to annealing, constant-temperature based annealing gives better control over the annealing process and, at least in the case under study, results in attainment of the preferred geometry of the system more efficiently.