FIRST PRINCIPLES CALCULATION OF THE ELECTRONIC AND STRUCTURAL PROPERTIES OF USn3 USING LDA+U METHOD

The actinide compounds exhibit a variety of unusual ground states. These states are dominated by the strong electron-electron correlations that are not included in normal density-functional electronic band-structure calculation with the local density approximation. These correlations are taken into account in the local density approximation +U (LDA+U) method. We have calculated the Coulomb repulsion term U for uranium in USn 3 compound, and investigated the total and partial DOS for USn 3 using LDA+U method. The LDA+U results for USn 3 have been compared with similar results from a ThSn 3 model calculation through which the number of 5f electrons outside the U muffin-tin sphere in USn 3 has been deduced. We have also calculated the electric field gradient (EFG), which may be regarded as a measure of the asymmetry in charge distribution, at the Sn site in USn 3 in LDA , LDA+SO and LDA+SO+U methods, and have shown that the Coulomb repulsion term does not introduce any considerable effect on the electric field gradient at the Sn site.