Electronic Structures and Properties of Actinide‐Bimetal Compounds An2O2 (An=Th to Cf) and U2E2 (E=N, F, S)

Abstract

AbstractIn this study, we investigated the geometry structure and the chemical bonding of actinide clusters An2O2 by quantum chemistry calculations. Through the geometry searching for An2O2 clusters with the combination of considerable initial structures and spin states, it is found that a novel ground‐state structure of quasi‐linear type for Pa2O2 compares with a rhombic structure for the rest of An2O2 clusters. Due to the more extended 5 f orbitals, the Pa−Pa bond is verified to be a triple bond by the electronic configuration and the bond order analysis, which brings the quasi‐linear structure of Pa2O2 and distinguishes it from the rhombic ones. For both kinds of ground‐state structures, the participation of 5 f orbitals in the An−O bonds stabilizes the structures further. Owing to spin‐orbit coupling, the ground‐state structure of U2O2 changes from the linear one at the SR level to the rhombic one with SO into consideration. Further investigations on clusters U2E2 with different ligands reveal that the quasi‐linear U2F2 has an equivalent quadruple bond. The decline of the bonding electrons of the U−U bond, the foremost causes for the change of the structures and illustrates the decrease of the U−U bond strength. Our investigations on An2O2 and U2E2 compounds provide some insights into the role of 5 f orbital in the chemical bonding of actinide compounds and f‐f bonding in multiple bonding.