Theoretical analysis of electronic structure for the chemical bonding of Pu and Am in MgO

Tanaka, Kumiko; Hirata, Masaru ; Sekine, Rika*

The relativistic discrete-variational Dirac-Fock-Slater (DV-DFS) method was performed to investigate the electronic structure of MgO doped with Pu or Am atoms. The differences between these systems, in particular, the participation of d-electrons and f-electrons in chemical bonding, were clarified by calculating their electronic structures. Substitution of actinide atoms was found to result in the effective charges of MgO becoming smaller, with a large charge transfer occurring as far as the second layer. It was also found that the bonding feature between the center atom and the surrounding oxygen atoms was extended to lower energy in the case of actinide (An) substituted systems. Moreover, the bonding characteristics were assigned; a bonding interaction for An6d-O2p and an anti-bonding for An5f-O2p near the HOMO level. These complex effects were found to dominate the strength of the covalent bonding between MgO and actinide atoms.