Structural Evolution of Cadmium Selenide Clusters: An Unbiased Global Optimization Study of (CdSe) N for 5 ≤ N ≤ 80.

The structures of large cadmium selenide clusters are poorly understood due to the presence of challenging long-range Coulombic interactions and a vast number of possible structures. In this study, we present an unbiased fuzzy global optimization method that incorporates atom-pair hopping, ultrafast shape recognition, and adaptive temperatures within a directed Monte Carlo framework to enhance the search efficiency of binary clusters. Using this method and first-principles calculations, we successfully obtain the lowest-energy structures of (CdSe) N clusters with 5 ≤ N ≤ 80. The putative global minima reported in the literature have been obtained. The binding energy per atom tends to decrease with cluster size. Our results show that the stable structures evolve from rings to stacked rings, cages, nanotubes, cage-wurtzite, cage-core, and finally wurtzite structures, enabling us to reveal a systematic structural evolution for the growth of cadmium selenide clusters without ligands.