Energy minimization using the classical density distribution: Application to sodium chloride clusters

The adiabatic Gaussian density annealing (AGDA) optimization algorithm, based on direct integration of the classical Bloch equation is reciprocal temperature, is employed to study the structures of (NaCl)(n) and (NaClNa+ clusters. The results of the energy minimizations are compared with simulated annealing, using molecular dynamics. We model these clusters with a rigid core potential used in previous studies. Overall, the AGDA algorithm was successful in isolating the lowest-energy minima. In contrast to the conclusion of a previous study, we find that molecular-dynamics-based simulated annealing can be quite effective at isolating low-energy minima. However, the effectiveness of the method is strongly dependent on the integration algorithm employed. The hexagonal and cubic growth forms are found to be most stable for small clusters and the fee structure is most stable for large clusters in agreement with previous studies. The difficulty in locating the global energy minimum is explained in terms of the statistical properties of the energy landscape.