Unveiling a Novel, Cation-Rich Compound in a High-Pressure Pb–Te Binary System

[Image: see text] Because of the common oxidation states of group IV elements (+2 or +4) and group VI elements (−2), 1:1 and 1:2 are two typical stoichiometries found in the IV–VI compounds. Particularly, in the Pb–Te binary system, the 1:1 stoichiometric PbTe is believed to be the only stable compound. Herein, using evolutionary algorithms, density functional theory, a laser-heated diamond anvil cell, and synchrotron X-ray diffraction experiments, we discovered a novel Pb–Te compound with an unexpected stoichiometry of 3:2 above 20 GPa. This tetragonal Pb(3)Te(2) is the one of the very few cation-rich compounds that has ever been discovered in the entire IV–VI binary system. Further analyses based on electron density distribution, electron localization function, and Bader charge have shown that this newly discovered compound has a mixed character of chemical bonding with a decreased ionicity. By further calculating the electron–phonon interaction, Pb(3)Te(2) is predicted to exhibit a superconducting transition at low temperatures. The discovery of Pb(3)Te(2) paves the way for further explorations of other novel cation-rich IV–VI group compounds.