First-principles study of rare-earth-doped superconducting CaFe2As2

We report a systematic and ab initio electronic structure calculation of Ca 0.75M 0.25Fe 2As 2 with M = Ca, Sr, Eu, La, Ce, Pr, Nd, Pm, Sm, Na, K, Rb. The recently reported experimentally observed structural trends in rare earths-doped CaFe 2As 2 compounds are successfully predicted and a complete theoretical description of the pressure induced orthorhombic to collapsed tetragonal transition is given. We demonstrate that the transition pressure is reduced by electron doping and rises linearly with the ionic size of the dopants. We discuss the implications of our description for the realization of a superconducting phase