Mapping out reaction paths for conformational changes in (M g O) n clusters: a study based on a stochastic procedure

Abstract

Clusters can exhibit enormous structural diversities and in most cases with the increase in size, the number of conformers that can be supported by the potential energy surface describing the system also increases at a rapid rate. In the present work, this issue has been addressed from the angle of finding out transformation pathways or the so-called reaction paths for interconversion among isomers in (M g O) n clusters, where ‘n’ denotes the size. Clusters with ten different values of ‘n’ starting from 6 and ending at 16 have been studied. For each of these sizes, effort has been made to identify the transition state geometry which connects two minimum configurations. Structural similarities or dissimilarities between the various conformers have been discussed so as to see if any basic unit gets repeated with increase in size of the clusters. The entire study has been conducted using the stochastic optimisation principle of simulated annealing and an adequately defined objective function which can uniquely guide the search towards a first-order saddle point or the transition state on a potential energy surface.