Computational study of An-O bonding in ThO₂ bulk from hybrid density functional theory within an embedded cluster model

We construct a model for thorium dioxide bulk using hybrid density functional theory within the periodic electrostatic embedded cluster method. By substituting one Th with other actinides (An = Pa – Cm), we study and compare the An-O bonding properties. We observe that the An-O bonds transition from ionic to covalent along the An series, with covalent properties found for the An-O bonds from Pu onwards. Further, by substituting two neighbouring Th atoms with other actinides (Pa – Cm), we reveal the effects of neighbouring An atoms on the An f states and An-O bonds. These effects vary along the An series. Lastly, by
substituting two neighbouring Th atoms with one Pu and one other actinide (Pa, U, Np, Am, Cm), we study and compare the influence of the neighbouring An on Pu f states and Pu-O bonds. Our findings indicate that the energy of Pu f states can be manipulated by varying the neighbouring An atoms.