Observing the Role of Electron Delocalization in Electronic Transport by Incorporating Actinides into Ligated Metal-Chalcogenide Superatoms

Since delocalization of electronic states is a prerequisite for exerting unique electron transport properties, early actinides (An) with highly delocalized 5f/6d orbitals are natural candidates. However, given the experimental difficulties of such radioactive compounds and the complex relativistic effects in theoretical studies, understanding the electronic structure and bonding of actinides is underdeveloped on the periodic table. A further challenge is the very complicated electronic structures encountered in the confinement of actinides, as vividly illustrated by the weakly radioactive Th(Thorium)-encapsulated metal chalcogenide clusters, Th@Co₆Te₈L₆ (L = PH₃, PMe₃, PEt₃). Here we report the electronic structure and the electron transport properties of the Th@Co₆Te₈L₆ clusters and compare them with those of the hollow Co₆Te₈L₆ clusters using the nonequilibrium Green's function combined with relativistic density functional theory (NEGF-DFT). We found that the equilibrium conductance in Th@Co₆Te₈(PH₃)₆ (0.76 G₀) has been greatly improved over that in Co₆Te₈(PH₃)₆ (0.03 G₀), which has also been verified under an applied different bias voltage. The covalent bonding character between 6d (Th) and 3d (Co) atomic orbitals resulting from steric confinement is the source of the performance enhancement and a most important factor governing the accessibility of such 5f/6d orbitals. The results are of significance to the rapidly developing field of molecular nanoelectronics.