Hu SX, Liu HT, Cao LZ, Chen XT, Guan PF, Zhang P. Distinguishing the Geometric and Electronic Structures of Actinide Carbides An
xC
8 (An = Th, U;
x = 2, 3) through Exchange Interactions.
J Phys Chem A 2024;
128:829-839. [PMID:
38266177 DOI:
10.1021/acs.jpca.3c06060]
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Abstract
Global-minimum optimizations combined with relativistic quantum chemistry calculations have been performed to characterize the ground-state stable structures of four titled compounds and to analyze the bonding properties. Th2C8 was identified as being a ThC4-Th(C2)2 structure, U2C8 has been found to favor the U-U(C8) structure, and both Th3C8 and U3C8 adopt the (AnC3)2-(AnC2) structure. Then, the wave function analyses reveal that the interactions between the Th 7s-based orbital and the σg molecular orbital of the C2 unit compensate for the excitation energy of 7s16d1 → 6d2 and lead to the stabilization of two Th(IV)s in the ThC4-Th(C2)2 structure. It also reveals that the U species exhibit magnetic exchange coupling behavior in UxC8, for instance, as seen in the direct interaction of U2C8 and the superexchange pathway of U3C8, which effectively stabilizes their low-spin states. This interpretation indicates that the geometric and electronic structures of AnxC8 species are largely influenced by the local magnetic moment and spin correlation.
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