First-principles investigation of synergistic rattling and delocalization effects on ultralow lattice thermal conductivity and thermoelectric performance in Zintl phase RbSnSb
Phys. Rev. B 113, 094304 – Published 9 March, 2026
DOI: https://doi.org/10.1103/3gd5-6c96
Abstract
The thermoelectric properties of the Zintl compound RbSnSb are systematically investigated based on first-principles calculations. The delocalized nature of Rb atoms, together with the rattling vibrations of Sb atoms, induces pronounced lattice anharmonicity, driving the lattice thermal conductivity well below 1 W/mK. Due to strong optical-acoustic hybridization, acoustic modes are suppressed and optical phonons emerge as the dominant heat carriers, contributing more than 40% to and elucidating the microscopic origin of the ultralow thermal conductivity. In addition, the multivalley electronic structure enhances the power factor, while spin-orbit coupling reconstructs the band structure and mitigates the adverse effect of piezoelectric scattering in the noncentrosymmetric lattice. Benefiting from these synergistic features, RbSnSb achieves a remarkable figure of merit reaching 4.89 at 900 K, underscoring its promise as a high-performance thermoelectric material.
