Basic mechanisms of Frenkel pair recombinations in UO 2 fluorite structure calculated by molecular dynamics simulations

In the present paper, the analysis of Frenkel pair recombinations is investigated by empirical-potential-molecular dynamics simulations. Frenkel pairs with separation distance between the vacancy and the interstitial up to 1.5 times the lattice parameter have been studied. For each Frenkel pair, their lifetimes as a function of the temperature and their migration paths are analyzed. For both uranium and oxygen defects, the picture of the recombination is rather complex and depends on the separation distance and the structure. A thermal dependence on the recombination lifetimes is found in separation distance larger than 7 A. The energy that an interstitial must overcome to recombine with a vacancy is lower than the migration energy of the diffusion. This recombination activation energy is also related to the pathways of the vacancy hops during the recombinations. Recombination distances are discussed and compared with the results from previous displacement cascade simulations. Finally, the role of Frenkel pair recombinations on the resistance to amorphization in UO{sub 2} is discussed.

[1]  Hartmann,et al.  Radiation tolerance of complex oxides , 2000, Science.

[2]  J. Delaye,et al.  Displacement cascades in a borosilicate glass: Influence of the level of polymerization on the cascade morphology , 1998 .

[3]  J. Crocombette,et al.  Atomistic simulation of amorphization thermokinetics in lanthanum pyrozirconate , 2006 .

[4]  L. Hobbs.  Topology and geometry in the irradiation-induced amorphization of insulators , 1994 .

[5]  L. V. Brutzel,et al.  Displacement cascade initiated with the realistic energy of the recoil nucleus in UO2 matrix by molecular dynamics simulation , 2006 .

[6]  V. Kuzovkov,et al.  Phenomenological kinetics of Frenkel defect recombination and accumulation in ionic solids , 1992 .

[7]  R. Ewing,et al.  Ion-beam-induced amorphization and order-disorder transition in the murataite structure , 2005 .

[8]  W. J. Weber,et al.  Molecular dynamic simulation of disorder induced amorphization in pyrochlore. , 2005, Physical review letters.

[9]  Kostya Trachenko,et al.  Understanding resistance to amorphization by radiation damage , 2004 .

[10]  J. Delaye,et al.  A new empirical potential for simulating the formation of defects and their mobility in uranium dioxide , 2003 .

[11]  R. Ewing,et al.  Micro-structures associated with uraninite alteration , 2000 .

[12]  L. V. Brutzel,et al.  Molecular dynamics simulation study of primary damage in UO2 produced by cascade overlaps , 2006 .

[13]  L. Malerba,et al.  Basic mechanisms of atomic displacement production in cubic silicon carbide: A molecular dynamics study , 2002 .

[14]  Marc Hou,et al.  Comparison of interatomic potentials for UO2. Part I: Static calculations , 2007 .

[15]  H. Matzke,et al.  ION-BOMBARDMENT-INDUCED RADIATION DAMAGE IN SOME CERAMICS AND IONIC CRYSTALS: DETERMINED BY ELECTRON DIFFRACTION AND GAS RELEASE MEASUREMENTS , 1966 .

[16]  Fei Gao,et al.  Recovery of close Frenkel pairs produced by low energy recoils in SiC , 2003 .