Change of Fermi Surface Topology in CeRu2Si2 Studied by LSDA plus U Method

The detailed electronic structures of CeRu2Si2 have been investigated for a nonmagnetic state and a magnetic state under magnetic fields by in LSDA+U method. It is found that the Si position in the crystal structure is an essential parameter to reproduce precise topology of the experimentally determined Fermi surfaces of non-f reference LaRu2Si2. As for CeRu2Si2, the LDA calculation Lids to predict the nonmagnetic round state, which is experimentally reported to be Mainly occupied by vertical bar j = 5/2.j(z) = +/- 5/2 > orbitals, and the Fermi surfaces. The nonmagnetic case solution of LSDA+U method greatly improves the electronic structure in the nonmagnetic CeRu2Si2. An LSDA+U method is also applied to investigate the electronic Structure under applied magnetic fields, then the change of the so-called large Fermi Surfaces to small Fermi surfaces is Successfully described.