Simulation of ion-track ranges in uranium oxide

Abstract

Direct comparisons between statistically sound simulations of ion-tracks and published experimental measurements of range densities of iodine implants in uranium dioxide have been made with implant energies in the range of 100-800 keV. Our simulations are conducted with REED-MD (Rare Event Enhanced Domain-following Molecular Dynamics) in order to account for the materials structure in both single crystalline and polycrystalline experimental samples. We find near-perfect agreement between REED-MD results and experiments for polycrystalline target materials.

Pathway and energetics of xenon migration in uranium dioxide

“…Because of the difficulty of measuring atomic scale properties, calculating these properties in UO 2 has been of interest using both Density Functional Theory (DFT) 7,10,11,12,13,14,15,16,17,18,19 as well as empirical potentials. 8,9,11,12,19,20,21,22,23 Several theoretical investigations of xenon in UO 2 have studied diffusion via a tetravacancy (TV, 2 V U + 2 V O ) mechanism. 7,8,9 These previous investigations have proposed a variety of diffusion pathways for xenon using empirical potentials, Nudged Elastic Band (NEB), and constrained relaxations.…”

Experimental evidence of Xe incorporation in Schottky defects in UO2

“…%) in a heavy matrix like UO 2 , the xenon behavior (incorporation sites, pathways, and energetics of its migration) in UO 2 have been determined only using both density functional theory (DFT) [21][22][23][24][25][26][27][28][29][30] and empirical potentials. 11,26,[29][30][31][32][33][34][35][36][37][38] The incorporation site and diffusion mechanisms have not unambiguously determined even if authors generally agree with the fact that due to steric constraints, vacancy trap sites are favored over interstitial sites. However, no clear experimental evidence has been provided yet.…”

An improved interatomic potential for xenon in UO2: a combined density functional theory/genetic algorithm approach

“…Figure 3 shows relaxation energy error described by equation (10) for xenon defects in different incorporation sites. As with the defect energy comparison above, the IPR potentials perform the best, even for defect configurations for which IPR was not fit.…”

“…There have been many studies of xenon in UO 2 using density functional theory (DFT) [1][2][3][4][5][6][7][8][9], which can achieve good defect energetics, but DFT is too computationally demanding for large systems such as xenon bubbles in UO 2 . Interatomic potentials, on the other hand, enable calculations of larger systems and long molecular dynamics simulations [2,3,[10][11][12][13][14][15][16]. There have been many interatomic potentials parameterized for UO 2 [12,13], but only a few for xenon in UO 2 , despite the crucial role of xenon in the failure of nuclear fuels.…”