A universal COMB potential for the whole composition range of the uranium oxygen system

Abstract An empirical molecular dynamics potential in the Charge-Optimized Many-Body (COMB) formalism that covers the whole uranium-oxygen composition range has been developed. Extended from a previous potential for uranium metal, this universal U O potential is able to model more than 20 phases of uranium oxides. The potential's flexibility, accuracy and transferability have been fully verified by rigorous testing and comparison with ab-initio calculations and experimental measurements. It is shown to be one of the most versatile and high-quality UO2 potentials, the first potential for U4O9, U3O7 and UO3, and the first usable U3O8 potential. Many important properties of major oxides in the U O phase diagram have been calculated and critically reviewed, including the cohesive energy, formation/reaction energies, lattice parameters, elastic constants, bulk/shear moduli, and energies for non-stoichiometric point defects and stoichiometric defects pairs. Due to its special design and parameterization process, this U O potential is shown to outperform all other existing ones by either obtaining higher accuracy for many of these quantities, or exclusively being able to calculate some of them. The successfully development of this potential provides a useful, reliable and convenient tool for molecular dynamics simulations that are previously impossible or unreliable to do for many materials in the U O system. Correction for several published oxide structures is also included in the appendix.