Modelling the electronic structures and magnetic properties of LiFeAs and FeSe using hybrid density functional theory

The electronic structure and magnetic properties of iron-base superconductors including lithium-iron-arsenic (LiFeAs) and iron-selenium are studied using density functional theory and hybrid functional. It is found that the first-nearest neighbour exchange interaction is $∼ 16$ meV and $∼ 6$ meV for LiFeAs and FeSe respectively, and the second-nearest neighbour exchange $∼ 81$ meV and $∼ 13$ meV for LiFeAs and FeSe respectively. These results are in agreement with previous theoretical calculations and partly with experiments. The total energies for LiFeAs of different spin configurations including spin-0, spin-1, and spin-2 are also calculated. The lowest state is spin-2 state for LiFeAs. The electronic states for the ferromagnetic configuration of LiFeAs and FeSe also show half-metal beviour.