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A Density functional theory investigation of the reactions of Fe and FeO$$_{2}$$ with O$$_{2}$$

Fe及びFeO$$_{2}$$のO$$_{2}$$分子との反応に関する密度汎関数法による研究

中沢 哲也; 加治 芳行  

Nakazawa, Tetsuya; Kaji, Yoshiyuki

Fe及びFeO$$_{2}$$とO$$_{2}$$の反応過程と反応生成物をB3LYP/6-311+G(d)のレベルで調べた。これらの反応はポテンシャルエネルギー曲線、反応種間の相互作用エネルギー、Fe原子とO$$_{2}$$分子の励起に必要なエネルギーを求め、それらをもとに反応過程を検討した。反応生成物のNBO及びMulliken解析と振動計算も行った。基底状態のFe原子とO$$_{2}$$は障壁エネルギーを伴う非断熱的遷移や垂直励起エネルギーによるFe(O$$_{2}$$)からの遷移によってOFeOは形成される。この結果はFe原子とO$$_{2}$$分子は低温ではなく高温で反応することを示している。また、OFeOとO$$_{2}$$は吸熱的反応によって$$eta^{2}$$-及び$$eta^{1}$$-(O$$_{2}$$)FeO$$_{2}$$複合体を生成する。さらに、低い光エネルギーが複合体間での可逆遷移を可能にしている。得られた生成物のNBO解析から、生成物の原子電荷はFeとOの間で生じる電子移動や反応種(Fe$$^{+}$$, O$$_2^{-}$$)本来のイオン的特性に由来することがわかった。

The reactions of Fe and FeO$$_{2}$$ with O$$_{2}$$ and the products of these reactions are investigated at the B3LYP/6-311+G(d) level. The reactions are considered in terms of the calculated potential energy surfaces, the interaction energies between reactant species, and the energies required to populate the higher electronic states such as the excited states of Fe($$^{5}$$F, $$^{3}$$F) and O$$_{2}$$($$^{1}$$$$Sigma$$$$_{rm g}^+$$). It is found that the reactions of Fe with O$$_{2}$$ are endothermic and that the direct formation of dioxide OFeO is due to an ionic interaction of Fe$$^{+}$$ with O$$_2^{-}$$. Furthermore, the diabatic transitions from the covalent and ionic surfaces onto another ionic surface with energy barriers allow the Fe + O$$_{2}$$ reaction to proceed toward the formation of OFeO. There are other paths corresponding to the vertical excitation from peroxide Fe(O$$_{2}$$) to dioxide OFeO. The OFeO + O$$_{2}$$ reactions are found to endothermically produce the $$eta$$2- and $$eta^{1}$$-(O$$_{2}$$)FeO$$_{2}$$ complexes, and the low-lying states of complexes are found to be closely located in energy. The CCSD and CCSD(T) single point energy calculations are performed with the structures optimized at the B3LYP level. The results of NBO and Mulliken analyses and the harmonic vibrational frequencies are presented.

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パーセンタイル:27.34

分野:Materials Science, Multidisciplinary

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