CRYSTAL-CHEMISTRY AND STRUCTURES OF LEAD-ANTIMONY SULFIDES

Using chemical and topological rules to describe the structural chemis try of Pb2+ and Sb3+, we show that the substitution of Sb3+ into PbS ( galena) results in four possible topological series of structures, and that the conflicting requirements of chemical bonding and charge neut rality severely limit the number of structures that can occur in each series. The model accounts for the existence of most of the compounds found in the pure Pb-Sb-S phase diagram. It correctly predicts the dis tribution of Pb2+ and Sb3+ over the various cation sites and shows why the mirror plane is lost in some phases.