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

Pu, Am置換MgOの電子状態

田中 久美子; 平田 勝 ; 関根 理香*

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

本研究ではPu, Am原子で置換したMgOについて電子状態計算を行い、特に6d, 5f電子がどのように化学結合に関与するかを詳しく検討することを目的としている。計算方法には、相対論DV-DFS法を用いた。Mgをアクチノイドで置換すると、基盤MgOのイオン結合性が弱くなり、広い範囲にわたって電荷移動が起こることが推測された。また、MgO中でのAn間の有効電荷を比較すると、Pu原子がよりイオン性が大きいということがわかった。An-Oの結合の安定性を決める指標としては、An6d-O2pの結合性、及び、An5f-O2pのHOMO付近の反結合性という2つの因子が重要ではないかと考えた。

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.