Monte Carlo growth method: Application to molecular clusters

The Monte Carlo growth method (MCGM), a recently developed method of Potential Energy Surface (PES) exploration, is adapted to the case of molecular clusters. The choice of the relevant parameters of this method for the study of these systems is discussed. The MCGM is applied to two different molecular systems: the acetonitrile and the molecular nitrogen 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 is much more effective than the MCSA and yields similar results to those of the DQM, without needing any initial cluster guess. Obtained isomers for clusters up to (CH3CN)(6) and (N-2)(14) are described. In both systems, remarkably stable patterns are observed: the anti-parallel pair in the case of the acetonitrile, the pentagonal bipyramid and the icosahedron for nitrogen clusters. Lowest-energy isomers of (N-2)(n) clusters are isomorphic to those of Ar-n.