First-Principles Study of Barium and Zirconium Stability in Uranium Mononitride Nuclear Fuels

Abstract

Barium and zirconium solution behaviors in antiferromagnetic uranium mononitride (UN) have been studied based on first-principles density functional theory. By calculating the incorporation and solution energies in UN, it is found that the most favorable solution sites are U vacancies for both Ba and Zr, and Zr is more soluble than Ba. The volume of the Ba-doped system keeps expanding with increasing Ba doping concentration, whereas that of the Zr-doped system changes from swelling to contraction with increasing Zr doping concentration. This phenomenon may result from the difference of these two elements in atom radius and coordination mechanism. Furthermore, the solution energies of metallic and nitride phases of Ba and Zr indicate that both phases of Ba are insoluble in the UN matrix, whereas the metallic phase of Zr is insoluble, and its nitride ZrN is soluble in the UN matrix.

Theoretical Investigation on Incorporation and Diffusion Properties of Xe in Uranium Mononitride

“…For example, using conventional DFT, the ground state of UN was predicted to be ferromagnetic, which is contradicted with the experimentally observed antiferromagnetic order. 14,20 Herein, the DFT+U scheme has been used to consider the strong on-site Coulomb repulsion among the localized U 5f electrons, the details of which has been displayed elsewhere by Gryaznov et al 14 As described in our previous work, 21 the Hubbard U and J parameters for UN were set to be 2.50 and 0.51 eV, respectively. 21 In addition, the quasi-annealing approach was applied herein to solve the notorious metastable states problem encountered in the DFT+U method.…”

Transport properties in dilute UN(X) solid solutions (X=Xe,Kr)

“…Point defects in UN have been investigated with various methods, using either GGA or GGA+U or interatomic potentials to compute the formation energies of various vacancy, antisite, Frenkel and Schottky defect configurations [14][15][16] . They were found to be different depending on the studies and methods used, but in the most comprehensive of them 15 , the formation energy of a U vacancy, a N vacancy and a Schottky defect were found to be, respectively, 6.89 eV, 7.81 eV and 13.81 eV, using GGA+U (U eff =1.85 eV) and the isolated atoms as reference states.…”

Adsorption and dissociation of H2O on the (001) surface of uranium mononitride: energetics and mechanism from first-principles investigation

“…In recent years, the UN bulk has been widely investigated by using density function theory (DFT) and DFT+U methods. 1,[13][14][15][16][17][18][19] For example, Modak et al 13 investigated the electronic, vibrational, elastic, and structural properties of UN over the pressure region of 0-100 GPa by using the DFT method. Gryaznov et al 1 studied the atomic, electronic and low temperature magnetic structure of UN by using the DFT+U method.…”

“…Gryaznov et al 1 studied the atomic, electronic and low temperature magnetic structure of UN by using the DFT+U method. In our recent studies, using the DFT+U method, we have investigated the influence of intrinsic point defects on the properties of UN, 15 the atomic behaviors of barium and zirconium in UN, 16 and the incorporation and diffusion behaviors of Xe in UN, 17 respectively. However, as far as we know, only several studies have been performed on the UN surfaces by using the first-principles method.…”