Rational Analyses of Heat Capacity for Thermoelectric Materials

Proper data analysis is essential to extracting meaningful insights from raw data. For thermoelectric materials, specific heat measurements provide important clues to thermal properties and are routinely analyzed using the Debye–Einstein model. Conventional treatments often rely on intuition concerning the number of Einstein modes and the temperature range analyzed, thereby potentially making the conclusions user-dependent. In this Perspective, we propose a rational basis that guides the selection of the optimal number of Einstein oscillator terms within a specified temperature range, allowing for robust conclusions. We demonstrate that the results obtained within this approach align remarkably well with the theoretically calculated phonon dispersions, enabling the accurate identification of the flat bands that contribute to the specific heat. Our method can be successfully applied to materials with stereochemically active lone pairs (PbBi 2 S 4, PbSnS 3, TlBiSe 2, and AgPbBiSe 3 ), intrinsic rattler species (TlCuZrSe 3 and Bi 13 S 18 Br 2 ), soft chemical bonding (CuBiI 4 ), and materials with nanoscale atomic ordering (Cd-doped AgSbTe 2 ), demonstrating its broad applicability.