Theoretical study on the reaction between uranium and O₂

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• 作者：Shuai ; Maobing ; Hairong ; Hu ; Xin ; Wang ; Pengji ; Zhao ; Anmin ; Tian
• 关键词：Uranium oxidation ; Ab initio ; Mulliken population analysis ; Potential energy surface ; 5f electrons
• 刊名：Journal of Molecular Structure: THEOCHEM
• 出版年：2001
• 出版时间：February 28, 2001
• 年：2001
• 卷：536
• 期：2-3
• 页码：269-276
• 全文大小：486 K

文摘

Investigating the electronic structure of the products of uranium oxidation and the electron transfer in this process, and revealing the mechanism on the initial oxidation stage of uranium surface are of great importance for finding out the effective anti-corrosion methods of uranium surface. In this paper, optimized geometries, total energies and electronic structures of some gaseous atoms and molecules of uranium–oxygen system are calculated with harmonic vibration analyses using ab initio method. Some potential energy surfaces (PESs) of the uranium oxidation process are also constructed. The calculated geometric parameters and infrared vibrational frequencies of some uranium oxides are consistent very well with experimental data. The PESs show that different reaction modes result in different product geometries. When U approaches O₂ at the oxygen atom top along the axis of O–O bond, a relatively stable linear structure, O–O–U, is formed, which has the possibility to decompose to UO and O. When U approaches O₂ along the perpendicular median of the O–O bond axis, a stable molecule UO₂ comes into being via two bent metastable structures with bond angles of about 151 and 105°, respectively. No potential energy barrier is needed for the uranium and O₂ to form the metastable states, while a very little barrier is needed to form the stable linear UO₂ from the metastable structures. And for the reaction O+UO→OUO (linear) also, there is no potential energy barrier needed, while for the reaction O+OU→UOO (linear), a barrier of about 4.5eV is needed. U5f atomic orbital electrons dominate in the formation of the U–O bonds.