QUANTUM MONTE CARLO VIBRATIONAL DYNAMICS IN A PROPERTY-BASED INTERACTION POTENTIAL SCHEME FOR WEAKLY BOUND CLUSTERS

摘要

The typical shallowness of the potential surfaces of weakly bound clusters implies sizable ground-state vibrational excursions in the weak modes, a feature often complicated by considerable anharmonicity. The difficulties of vibrational analysis are exacerbated as the number of weak modes increases with the number of molecules in a cluster. Quantum Monte Carlo (QMC) approaches offer a general suitability to the problem of vibrational dynamics of weakly bound clusters in that they can fully account for anharmonicity and large amplitude motions. We report on the effectiveness and convergence behavior of diffusion quantum Monte Carlo for both energies and the key spectroscopic values of vibrationally averaged rotational constants. QMC involves recurring evaluations of the interaction potential, and we show how property-based, two- and three-body potentials (e.g.,those involving intrinsic molecular tensor properties) may be carefully Linked to the QMC propagation steps. (C) 1997 by John Wiley & Sons, Inc. [References: 34]