  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. We discuss the influence of these
properties on the formation of superconductivity and in particular we find
evidence that both magnetic and lattice interactions may be important to the
formation of superconductivity. We also find that the Local Spin Density
Approximation is able to accurately predict the ordering moment in the low
temperature orthorhombic phase.

Strongly Correlated Electrons;Superconductivity