锆掺杂二氧化铀中氧缺陷扩散机制的密度泛函计算研究

应用基于量子力学的密度泛函计算和过渡态搜寻的CI-NEB方法，研究了锆掺杂前后二氧化铀晶格中氧空位和氧间隙本征缺陷的扩散机理，计算了扩散路径和扩散能垒。计算结果表明，锆掺杂使得氧空位缺陷<100>方向的扩散能垒降低了0.40 eV，氧间隙交换机制的扩散能垒降低了0.07 eV。锆掺杂后，氧空位远低于氧间隙缺陷的扩散能垒。最后分析了扩散过程中氧原子和金属原子之间的键长，说明锆掺杂导致点缺陷扩散能垒降低与晶格畸变密切相关。Oxygen vacancy and interstitial diffusion mechanisms in uranium dioxide doped with zirconium are investigated by the density functional theory calculations. The migration pathways and barriers are identified using the climbing-image nudge elastic band (CI-NEB) method. It is found that the vacancy migration barrier along the <100> direction decreases by about 0.40 eV, while the indirect interstitial migration barrier decreases by about 0.07 eV in the zirconium doped uranium dioxide. The oxygen vacancy migration barrier is far lower than the oxygen interstitial migration barrier in the uranium dioxide doped with zirconium. Based on the analysis of bond length of local structures during the migration of oxygen atoms, it is concluded that the lattice distortion may be responsible for the reduction of oxygen migration barrier.

Migration Mechanism of Oxygen in Uranium Dioxide Doped with Zirconium

Oxygen vacancy and interstitial diffusion mechanisms in uranium dioxide doped with zirconium are investigated by the density functional theory calculations. The migration pathways and barriers are identified using the climbing-image nudge elastic band (CI-NEB) method. It is found that the vacancy migration barrier along the <100> direction decreases by about 0.40 eV, while the indirect interstitial migration barrier decreases by about 0.07 eV in the zirconium doped uranium dioxide. The oxygen vacancy migration barrier is far lower than the oxygen interstitial migration barrier in the uranium dioxide doped with zirconium. Based on the analysis of bond length of local structures during the migration of oxygen atoms, it is concluded that the lattice distortion may be responsible for the reduction of oxygen migration barrier.