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

AMn[sub 2]P[sub 2] (A = Sr, Ba) is an example of a composition that can assume a different structure type, depending on the identity of the cation. BaMn[sub 2]P[sub 2] crystallizes in the ThCr[sub 2]Si[sub 2] structure type, whereas SrMn[sub 2]P[sub 2] crystallizes in the CaAl[sub 2]Si[sub 2] structure type. These compounds have been characterized by temperature-dependent magnetic susceptibility, neutron diffraction, and resistivity. The results indicate that extended Hueckel calculations cannot adequately account for the electronic or magnetic properties of these compounds.