Structure prediction for nanoscale magic-size CdSe clusters from a new efficient structure-searching strategy

Magic-size clusters (MSCs), as crucial intermediates or by-products in quantum dot (QD) synthesis, have attracted significant attention due to their unique absorption peaks and high stability. However, the lack of single-crystal MSCs hinders a comprehensive understanding of their structures. In this study, we focus on structural searching and predictions for typical (CdSe)_n (n = 13, 19, 33, and 34) MSCs. We develop an efficient structure-searching workflow that integrates Ab Initio Random Structure Searching (AIRSS), the semi-empirical extended tight binding (xTB) method, and density functional theory (DFT). Our results reveal that the lowest energy isomers of these four (CdSe)_n clusters adopt a core@cage topology, differing from previously reported studies. Notably, the newly predicted stable structure of (CdSe)₃₄ features an adamantane-type Cd₄Se₆ core, which is identified for (CdSe)_n clusters for the first time. This efficient structure-searching strategy yields numerous novel and more stable structures for larger-sized CdSe MSCs. It is our hope to provide insights into their structures and potential transformation mechanisms from smaller to larger MSCs.