Energetics of solid-state metathesis reactions in nanostructured thermoelectric systems

Thermoelectric systems with large compositions of AB (e.g. SnTe) and much smaller compositions of A’B’ (e.g. CdS, ZnS) are promising candidates since the second-phase nanostructures scatter phonons, reducing lattice thermal conductivity and increasing ZT. In this work, we use high-throughput density functional theory (DFT) calculations to evaluate the metathesis reactions (AB+A'B'↔A'B+AB') of 1638 quaternary phase systems (A,A’)(B,B’) in order to understand the behaviors and predict potential nanostructured thermoelectrics. We include systems most relevant for rocksalt-based thermoelectrics: group II, IIb, and IV cations, and group VI anions. In addition, we include group III cations and group V anions as possible secondary phases. We find that the metathesis reactions exhibit well-defined trends, which can be explained within the context of hard-soft acid-base theory (HSAB). Deviations from these trends are examined in more detail and finite temperature effects are investigated for select systems.