The first-principles treatment of the electron-correlation and spin-orbital effects in uranium mononitride nuclear fuels

The DFT+U calculations were employed in a detailed study of the strong electron correlation effects in promising nuclear fuel -- uranium mononitride (UN). A simple method for solving the multiple minima problem in DFT+U simulations and insure obtaining the correct ground state is suggested and applied. The crucial role of spin-orbit interactions in reproduction of the U atom total magnetic moment is demonstrated. Basic material properties (the lattice constants, the spin- and total magnetic moments on U atoms, magnetic ordering, and the density of states) were calculated varying the Hubbard U-parameter. Varying the tetragonal unit cell distortion, the meta-stable states have been carefully identified and analyzed. The difference of the magnetic and structural properties obtained for the meta-stable and ground states are discussed. The optimal effective Hubbard parameter Ueff =1.85 eV reproduces correctly the UN anti-ferromagnetic ordering, and only slightly overestimates the experimental total magnetic moment of U atom and the unit cell volume.

GRYAZNOV Denis;  KOTOMIN E. A.;  HEIFETS E.; 

2012-04-20

ROYAL SOC CHEMISTRY

JRC68223

1463-9076,   

http://pubs.rsc.org/en/content/articlelanding/2012/CP/C2CP40297A,    https://publications.jrc.ec.europa.eu/repository/handle/JRC68223,   

10.1039/c2cp40297a,