Modelling the electronic structure and magnetic properties of LiFeAs and FeSe using hybrid-exchange density functional theory

摘要

The electronic structure and magnetic properties of LiFeAs and FeSe have beenstudied using hybrid exchange density functional theory. The total energies fora unit cell in LiFeAs and FeSe with different spin states includingnon-magnetic and spin-2 are calculated. The spin-2 configuration has the lowerenergy for both LiFeAs and FeSe. The computed anti-ferromagnetic exchangeinteractions between spins on the nearest (next nearest) neighbouring Fe atomsin LiFeAs and FeSe are approximately 14 (17) meV and 6 (13) meV respectively.The total energies of the checkerboard and stripe-type anti-ferromagneticordering for LiFeAs and FeSe are compared, yielding that for LiFeAs thecheckerboard is lower whereas for FeSe the stripe-type is lower. However, owingto the fact that the exchange interaction of the next nearest neighbour islarger than that of the nearest one, which means that the collinear orderingmight be the ground state. These results are in agreement with previoustheoretical calculations and experiments. Especially the calculations forLiFeAs indicate a co-existence of conducting d-bands at the Fermi surface andd-orbital magnetism far below the Fermi surface. The theoretical resultspresented here might be useful for the experimentalists working on theelectronic structure and magnetism of iron-based superconductors.