A Test of the Application of Extended Hückel Calculations to the ThCr2Si2 and CaAl2Si2 Structure Types: the Case of SrMn2P2 and BaMn2P2

AMn2P2 (A = Sr, Ba) is an example of a composition that can assume a different structure type, depending on the identity of the cation. BaMn2P2 crystallizes in the ThCr2Si2 structure type, whereas SrMn2P2 crystallizes in the CaAl2Si2 structure type. These compounds have been characterized by temperature-dependent magnetic susceptibility, neutron diffraction, and resistivity. The results indicate that extended Hückel calculations cannot adequately account for the electronic or magnetic properties of these compounds.