Dimensionality and magnetic interactions in CaFe2As2: An ab initio study

We present detailed electronic structure calculations for CaFe2As2. We investigate in particular the ‘collapsed’ tetragonal and orthorhombic regions of the temperature–pressure phase diagram and find properties that distinguish CaFe2As2 from other Fe-pnictide compounds. In contrast to the tetragonal phase of other Fe-pnictides the electronic structure in the ‘collapsed’ tetragonal phase of CaFe2As2 is found to be strongly 3D. By an analysis of the non-interacting susceptibility, χ0(q)χ0(q), of CaFe2As2 and LaFePO we discuss the role of magnetic interactions in iron-pnictides. From this we propose an intuitive explanation for the outstanding question relating to why the predicted antiferromagnetic moment depends strongly on coordinate relaxation and the choice of correlation functional.