A density functional method DFT/B3 p86 with relativistic effective core potential basis for U and 6-311+G( d) basis for O has been used to study HOMO energy levels, LUMO energy levels, energy gaps, and harmonic frequencies of UO3 ground state molecule under different inner radiation fields ranging from -0. 005 to 0. 005 a. u. . The results show that the magnitude and direction of the inner radiation fields have important effects on these characteristics of UO3 molecule. The harmonic frequencies ν2 ( b1 ) , ν3 ( a1 ) , ν4 ( a1 ) and ν6 ( b2 ) are close to experimental values 151. 5 cm-1 , 186. 2 cm-1 , 745. 7 cm-1 and 852. 6 cm-1 under different inner radia-tion fields. The HOMO energy level was found to decrease, but the LUMO energy level, energy gap and Fermi energy level were found to increase with increasing the inner radiation fields. The electron which occupies orbital is difficult to stimulate to empty orbital and transform into excited station. The UO3 molecular is more stable in inner radiation fields, it can prevent O2、H2 and so on to proliferate to superficial inner layer and corrode the ura-nium surface , which contributes to the uranium corrosion prevention in inner radiation fields.%铀原子和氧原子分别使用相对论有效原子实势(Relativistic Effective Core Potential)和6-311+G(d)基组,采用优选的密度泛函B3P86方法,研究了铀本身产生自辐射场(-0．005~0．005 a． u．)作用下UO3基态分子的最高占据轨道(HOMO)能级EH、最低空轨道(LUMO)能级EL、能隙Eg、费米能级FL 和谐振频率ν.结果表明：UO3分子在自辐射场中的谐振频率ν2( b1)、ν3( a1)、ν4( a1)和ν6( b2)与实验值151．5 cm-1、186．2 cm-1、745．7 cm-1和852．6 cm-1基本吻合. EH随自辐射场的增加而减少,EL随自辐射场的增加而增大,Eg 始终处于增大的趋势,费米能级FL上升,占据轨道的电子难以被激发至空轨道而形成激发态,UO3分子在自辐射场中更趋于稳定,可以阻止O2、H2等扩散到表面内层而腐蚀铀表面,有利于了铀在自辐射场中抗腐蚀.
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