Pauling’s Third Rule as a Guide for Designing Low Thermal Conducting Chalcogenides

Linus Pauling’s third empirical rule, which describes the destabilizing effect of shared polyhedral units in crystal structures, now provides a novel basis for understanding and predicting lattice thermal conductivity (κ lat ) in extended solids. In this perspective, we investigate ∼65 ternary metal chalcogenides with corner-shared (CS), edge-shared (ES), or face-shared (FS) polyhedral units, uncovering a monotonous decline in κ lat as polyhedral connectivity shifts from CS to ES to FS in the structure. This trend arises from increasing cationic repulsion, leading to local lattice instability and enhanced phonon scattering in structures particularly having either ES or FS polyhedra. Comparative analysis of metal chalcogenides having the same constituent atoms further validates that materials possessing ES and FS configurations consistently exhibit lower κ lat than materials having CS subunits. While a few exceptions exist, our findings establish Pauling’s third rule as a chemical guide for identifying materials with intrinsically ultralow κ lat, a key requirement for high thermoelectric performance. We believe that this insight would accelerate the discovery of efficient thermoelectric materials by leveraging fundamental crystal chemistry principles.