  We have performed a detailed analysis of the magnetic (collinear and
noncollinear) order and atomic and the electron structures of UO2, PuO2 and UN
on the basis of density functional theory with the Hubbard electron correlation
correction (DFT+U). We have shown that the 3-k magnetic structure of UO2 is the
lowest in energy for the Hubbard parameter value of U=4.6 eV (and J=0.5 eV)
consistent with experiments when Dudarev's formalism is used. In contrast to
UO2, UN and PuO2 show no trend for a distortion towards rhombohedral structure
and, thus, no complex 3-k magnetic structure is to be anticipated in these
materials.
