Phase relations between germanium, tin, and lead chalcogenides in pseudobinary systems containing orthorhombic phases

As an extension of our earlier studies of phase relations in pseudobinary systems of germanium, tin, and lead chalcogenides, we have calculated the T-x phase diagrams of all the pseudobinary systems formed by IV-VI compounds and containing orthorhombic phases: SnS-SnSe, SnS-SnTe, SnS-PbS, SnSe-SnTe, and SnSe-PbSe. In the calculations, we used a unified thermodynamic model and the same thermodynamic data for the end members of the pseudobinary systems. The interaction parameters were determined using the relationship, derived earlier for IV-VI compounds with cubic structures, between the excess Gibbs energy and the difference in chemical bonding between the end members of the systems, quantified by a combination of Simons-Bloch orbital radii.