First principles study of magnetic interactions and electronic structure in iron chalcogenide superconductors

By using first-principles density functional theory combined with linear response theory we investigate the magnetic interaction of the Fe chalcogenide high T$_C$ superconductors, FeSe$_{1-x}$Te$_x$. The calculated exchange interactions are found to be different from those in pnictides, which suggests possibly different superconducting properties. The nearest neighbor antiferromagnetic coupling ($J_{1a}$) is much stronger than the nearest neighbor ferromagnetic ($J_{1b}$) and the next nearest neighbor coupling ($J_2$). The $J_{1a}$ and $J_{2}$ gradually decreases as $x$ increases while $J_{1b}$ increases and becomes to be stronger than $J_{2}$. Total energy calculation results and the electronic structure will be presented and compared to recent experiments.