Previous experimental work has shown self-irradiation in Pu solids produces point defect populations that correlate with increases in local disorder, long-range structural changes, induced magnetic moments, and other thermo-physical property changes. Thermally activated kinetic processes drive these defects to diffuse and interact toward either damage evolution or lattice recovery. Using DFT and cNEB, as implemented in VASP, migration barriers for mono-vacancy and split-interstitial diffusion and Frenkel pair recombination were calculated in fcc δ-Pu. The results indicate the migration barrier of a monoclinic mono-vacancy is lower when compared to the migration barrier of a tetragonal split-interstitial in δ-Pu, contrary to typical fcc metal point defect migration. This fundamentally different diffusion mechanism is a result of local symmetry breaking induced by electronic and magnetic interactions leading to the development of Pu–Pu short bonds (<3.0 Å) within a many-atom complex defect forming and migrating. The migration of the monoclinic mono-vacancy maintains short bonds with anti-parallel spins throughout the transition; whereas, during the migration transition state for the tetragonal split-interstitial, formation of short bonds with parallel spins and a spin-flip of the migrating Pu interstitial occurs. The associated energy cost is reflected in an increase in the migration barrier energy. Frenkel pair recombination is not spontaneous at 0K, but correlates with magnetic moment interactions, leading to an energy barrier for recombination. From these results, it is concluded that migration of defects in unalloyed δ-Pu are highly dependent on the electronic and magnetic interactions that induce associated low-symmetry structures and consequently influence the diffusional properties. Typical fcc defect diffusion mechanisms do not apply to the monoclinic mono-vacancy and tetragonal split-interstitial in the complex 5f δ-Pu system suggesting that the experimental observation of radiation damage induced localized magnetic moments and anomalous diffusion properties measured in δ-Pu could be understood in terms of defect kinetics and interactions.

先前的实验工作表明，Pu固体中的自辐照会产生点缺陷，这些缺陷与局部无序增加，远距离结构变化，感应磁矩以及其他热物理性质变化相关。热活化的动力学过程驱使这些缺陷扩散并相互作用，从而导致损伤发展或晶格恢复。使用在VASP中实施的DFT和cNEB，在fccδ-Pu中计算了单空位和分裂间隙扩散以及Frenkel对重组的迁移壁垒。结果表明，与典型的fcc金属点缺陷迁移相反，与δ-Pu中的四方裂隙的迁移障碍相比，单斜晶单空位的迁移障碍要低。这种根本不同的扩散机制是由于电子和磁性相互作用引起的局部对称性破坏的结果，导致在许多原子复杂的缺陷形成和迁移过程中形成了Pu-Pu短键（<3.0Å）。单斜晶单空位的迁移在整个过渡过程中保持与反平行自旋的短键；相反，在四方裂隙的迁移过渡状态期间，发生了具有平行自旋和迁移的Pu隙的自旋翻转的短键的形成。相关的能源成本反映在迁移势垒能量的增加中。Frenkel对重组不是在0K时自发的，而是与磁矩相互作用相关，从而导致了重组的能垒。根据这些结果，结论是，非合金δ-Pu中缺陷的迁移高度依赖于电子和磁相互作用，这些相互作用会引起相关的低对称结构，从而影响扩散性能。典型的fcc缺陷扩散机制不适用于复合物5中的单斜晶单空位和四方裂隙˚F δ浦系统表明辐射损伤的实验观察诱导δ普测量局部磁矩和反常扩散性能可在缺陷动力学和相互作用来理解。