Prediction of Magnetic State of UO2 within Hubbard-corrected Density-Functional Theory: A self-consistent approach

The magnetic state of UO$_2$ was determined experimentally to be anti-ferromagnetic. Starting from this experimental fact, researchers have calculated other properties within the Hubbard-corrected density-functional theory, DFT+U. Up to now, the Hubbard parameters for UO$_2$ were usually so chosen that the calculations give good results for some experimental data. Also, to our knowledge there exists no valid theoretical research report on the energetically stable magnetic state of this system. In present work, employing the new method which is based on density-functional perturbation theory, we have determined self-consistently the Hubbard parameters and ground-state energies for UO$_2$ crystal in both ferromagnetic and anti-ferromagnetic configurations, and the calculated results show that UO$_2$ crystal energetically favors an anti-ferromagnetic state with a small energy difference. In all the calculations the PBE-sol approximation was used for the exchange-correlation energy functional.