Ground state of BaCoS2 as a set of energy-degenerate orbital-ordered configurations of Co2+ ions

Abstract
The linear muffin-tin orbital method in the local density approximation (LDA + U) explicitly considering Coulomb correlations has been applied to calculate the electronic structure, magnetic moments, and parameters of the Heisenberg exchange interaction for cobalt ions in BaCoS2. Five solutions close in total energy with various orbital ordering of Co2+ ions and almost identical spin magnetic moments μ = 2.32μB of the Co2+ ion 3d-shell have been found. The BaCoS2 ground state can be considered as a set of energy-degenerate orbital-ordered configurations of Co2+ ions in the high-spin state.