Structure and disorder resulting in ultralow thermal conductivity in the defect chalcopyrite AgInSnSe₄

Quaternary chalcogenides are attractive for a variety of technological fields of interest due to the diverse physical properties these materials possess. Herein, the structural and thermal properties of the disordered chalcopyrite AgInSnSe₄ are reported revealing a distinct relation between its structure and physical properties. Modeling of the experimental temperature-dependent thermal properties revealed an ultralow thermal conductivity (0.47 Wm⁻¹K⁻¹ at room temperature) due to lattice anharmonicity, a low speed of sound and a low Debye temperature. Moreover, first principles electronic structure calculations revealed that the Ag-Se tetrahedra within the crystal structure possess relatively weak bonds due to occupied antibonding states from p-d orbital hybridization, which suppress the thermal conductivity. In order to further quantify our findings, we extended our analyses to include comparisons with other ternary and quaternary adamantine materials, all of which possess a fourfold tetrahedral coordination of atoms, in revealing the origin of the thermal properties in AgInSnSe₄.