High-throughput screening for full Heusler compounds with ultralow lattice thermal conductivity

Full Heusler compounds have attracted significant attention in thermoelectric (TE) research due to their excellent electronic properties and high-TE power factor. However, their intrinsic lattice thermal conductivity (κ_L) remains relatively high, limiting their potential for TE device applications. In this work, we proposed a novel and effective high-throughput screening method with less ab initio calculations for identifying full Heusler materials with ultralow κ_L values, using lone pair electrons and atomic rattling as key criteria. Then, from 184,424 full Heusler candidates, LaGaTe₂ and LaInTe₂ are identified with significantly low κ_L values of 0.31 W m⁻¹·K⁻¹ and 0.39 W m⁻¹·K⁻¹, respectively. The origin of the ultralow κ_L values is attributed to strong optical phonon scattering induced by optical phonon softening, which is caused by reduced Ga/In-Te bonding stiffness from unstable anti-bonding states formed by the lone pair electrons of Ga⁺/In⁺ and Te 5p electrons. Optical phonon softening significantly increases the scattering channels for the optical phonons, enhancing the scattering rates and phase space. Furthermore, the loosely bonded Ga/In-Te interactions cause the Ga/In atoms to exhibit rattling behavior within the pseudo-cage, further enhances the anharmonicity of materials. This work not only highlights a new way for fast discovering desired materials with ultralow κ_L, but also provides two new materials which is ideal candidates for many energy fields applications.