Structures and stabilities of UPbn (n & LE; 18) clusters: A first-principles global optimization calculation

Endohedrally doped clusters have received much attention because they can act as superatoms and have great potential as the building blocks for cluster-assembled materials. We have carried out a comprehensive study based on the combination of the particle swarming optimization algorithm and the relativistic density functional theory, to obtain geometric structures and stabilities of lead (Pb) clusters doped with one uranium (U) atom. A gradual evolution pattern was observed with the increasing number of Pb atoms, from exohedrally doped structures to quasi-endohedral structures, and finally to endohedrally doped structures. At least 12 and 11 Pb atoms were necessary to encapsulate the U atom completely in the calculation without and with the spin-orbit coupling (SOC) effect respectively. The UPb16 cluster was represented as a highly stable endohedral cage structure with the U atom around its center. In addition, the crucial role of the SOC effect was emphasized. We hope that our findings will provide a fundamental understanding of actinide-doped lead clusters, which may be quite different from their light element analogues.

Automated summary

In this study, we used a combination of the particle swarming optimization algorithm and the relativistic density functional theory to investigate the geometric structures and stabilities of lead clusters doped with one uranium atom. We found that the structures of the clusters gradually evolved from exohedral to quasi-endohedral and finally endohedral as the number of lead atoms increased. The calculation showed that at least 12 and 11 lead atoms were needed to completely encapsulate the uranium atom without and with the spin-orbit coupling effect, respectively. The UPb16 cluster was identified as a highly stable endohedral cage structure with the uranium atom at its center. The importance of the spin-orbit coupling effect was also emphasized. We hope that our findings will contribute to a better understanding of actinide-doped lead clusters, which may exhibit different behaviors compared to their light element analogues.