Structure Prediction for Nanoscale Magic-Size CdSe Clusters from a New Efficient Structure-Searching Strategy

Abstract

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, 34) MSCs. We develop an efficient structure-searching workflow that integrates Ab Initio Random Structure Searching (AIRSS), the semiempirical 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 size MSCs.