Density functional calculations of the electronic structure and magnetism of the different phases of

We have carried out noncollinear electronic structure calculations to investigate the structural, electronic and magnetic properties of the low-temperature orthorhombic and high-temperature tetragonal phases of BaFe 2 As 2 . We find that the GGA optimized orthorhombic phase has an LDA magnetic moment of 0.46 μ B in excellent agreement with the Mössbauer spectroscopy value of approximately 0.4 – 0.5 μ B per Fe atom. The very low LDA magnetic moment of 0.02 μ B for the Fe atoms in the GGA optimized tetragonal phase is consistent with the experimentally observed Pauli paramagnetism of the tetragonal phase. Thus, these calculations offer an improvement in the description of the Fe–As interaction in the 122 pnictide compound family.