title: A charge-optimized many-body potential for the U-UO2-O2 system.
abstract: Building on previous charge-optimized many-body (COMB) potentials for metallic α-U and gaseous O2, we have developed a new potential for UO2, which also allows the simulation of U-UO2-O2 systems. The UO2 lattice parameter, elastic constants and formation energies of stoichiometric and non-stoichiometric intrinsic defects are well reproduced. Moreover, this is the first rigid-ion potential that produces the correct deviation of the Cauchy relation, as well as the first classical interatomic potential that is able to determine the defect energies of non-stoichiometric intrinsic point defects in UO2 with an appropriate reference state. The oxygen molecule interstitial in the α-U structure is shown to decompose, with some U-O bonds approaching the natural bond length of perfect UO2. Finally, we demonstrate the capability of this COMB potential to simulate a complex system by performing a simulation of the α-U + O2 → UO2 phase transformation. We also identify a possible mechanism for uranium oxidation and the orientation of the resulting fluorite UO2 structure relative to the coordinate system of orthorhombic α-U.
authors.affiliation: Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Yangzhong
authors.initials: Y
authors.lastname: Li
authors.forename: Tao
authors.initials: T
authors.lastname: Liang
authors.forename: Susan B
authors.initials: SB
authors.lastname: Sinnott
authors.forename: Simon R
authors.initials: SR
authors.lastname: Phillpot
mesh_terms: D003198:Computer Simulation; D008956:Models, Chemical; D010084:Oxidation-Reduction; D013816:Thermodynamics; D014501:Uranium / Q000737:chemistry*; D017974:Uranium Compounds / Q000737:chemistry*
chemical_list: D017974:Uranium Compounds; D014501:Uranium; C012597:uranium dioxide