MONTE-CARLO GROWTH METHOD - APPLICATION TO MOLECULAR CLUSTERS

The Monte Carlo growth method (MCGM), a recently developed method of P otential Energy Surface (PES) exploration, is adapted to the case of m olecular clusters. The choice of the relevant parameters of this metho d for the study of these systems is discussed. The MCGM is applied to two different molecular systems: the acetonitrile and the molecular ni trogen clusters. The MCGM is compared to two classical PES exploration methods: the Monte Carlo simulated annealing technique (MCSA) and the dynamic quenching method (DQM) used in Molecular Dynamics. The MCGM i s much more effective than the MCSA and yields similar results to thos e of the DQM, without needing any initial cluster guess. Obtained isom ers for clusters up to (CH3CN)(6) and (N-2)(14) are described. In both systems, remarkably stable patterns are observed: the anti-parallel p air in the case of the acetonitrile, the pentagonal bipyramid and the icosahedron for nitrogen clusters. Lowest-energy isomers of (N-2)(n) c lusters are isomorphic to those of Ar-n.