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

We performed a simulation of a cluster of five water molecules at 300 K usi ng an ab initio potential. In our first study, the interactions were calcul ated at the Hartree-Fock level using a 6-31G* basis set. A parallel big mov e (hybrid) Monte Carlo algorithm was used to conduct this modeling. We comp ared the results obtained for this "quantum" system with those obtained fro m a conventional simulation employing an effective pair potential. We also estimated properties of the quantum system in terms,of the configurations g enerated by the conventional simulation by employing the appropriate Boltzm ann weighting. These estimates are in good agreement with those obtained fr om the full quantum simulation. We then repeated the Boltzmann weighting me thod, but this time using the BLYP density functional in our ab initio calc ulations, so as to include correlation effects. (C) 1999 John Wiley & Sons, Inc.