Monte Carlo simulations of water clusters on a parallel computer using an ab initio potential

We have performed a simulation of a cluster of five water molecules at 300 K in which the potential at each step was calculated at the Hartree-Fock level using a 6–31G∗ basis set. A parallel big move (hybrid) Monte Carlo algorithm was used to conduct this modelling. We compare the results obtained for this ʹquantumʹ system with those obtained from a conventional simulation employing an effective pair potential. We also estimate properties of the quantum system in terms of the configurations generated by the conventional simulation by employing the appropriate Boltzmann weighting. These estimates are in good agreement with those obtained from the full quantum simulation.