CONSTRUCTION OF SIMULATION WAVE-FUNCTIONS FOR AQUEOUS SPECIES - D3O+

This paper investigates Monte Carlo techniques for construction of com pact wave functions for the internal atomic motion of the D3O+ ion. Th e polarization force field models of Stillinger et al. and of Ojamae e t al. were used. Initial pair product wave functions were obtained fro m the asymptotic high temperature many-body density matrix after contr action to atom pairs using Metropolis Monte Carlo. Subsequent characte rization shows these pair product wave functions to be well optimized for atom pair correlations despite that fact that the predicted zero p oint energies are too high. The pair product wave functions are suitab le to use within variational Monte Carlo, including excited states, an d density matrix Monte Carlo calculations. Together with the pair prod uct wave functions, the traditional variational theorem permits identi fication of wave function features with significant potential for furt her optimization. The most important explicit correlation variable fou nd for the D3O+ ion was the vector triple product r(OD1) . (r(OD2) X r (OD3)). Variational Monte Carlo with 9 of such explicitly correlated f unctions yielded a ground state wave function with an error of 5-6% in the zero point energy. (C) 1998 American Institute of Physics. [S0021 -9606(98)51144-0].