Low Lattice Thermal\nConductivity and Anisotropic Thermal\nTransport Properties of the Layered BiAgOTe Material in Consideration\nof Four-Phonon Scattering: A First-Principles Investigation

Inspired by the excellent thermal transport properties\nof layered\nBiCuOX (X = S, Se, Te) materials, the electronic structure, mechanical,\nand thermal transport properties of isostructural Ag-based BiAgOTe\nmaterial are investigated using the first-principles calculations\nin combination with the Boltzmann transport theory. Layered BiAgOTe\nmaterial is an indirect bandgap semiconductor with a bandgap of 1.19\neV using the Heyd–Scuseria–Ernzerhof (HSE06) functional.\nThe elastic constants and shear modulus of the BiAgOTe material satisfy\nthe Born–Huang criterion, highlighting the high mechanical\nstability and pronounced shear resistance. Phonon dispersion curves\nand ab initio molecular dynamics simulations also demonstrate the\nhigh dynamic and thermal stabilities of the BiAgOTe material. Due\nto the specificity of the layered configuration, the BiAgOTe material\nexhibits pronounced anisotropy in lattice thermal conductivity and\nmechanical properties along the <i>a</i>- and <i>c</i>-directions. The weak interlayer interactions, coupled with a low\nYoung’s modulus, give rise to significant anharmonicity in\nthe BiAgOTe compound. The strong phonon scattering rate, large Grüneisen\nparameter, and small phonon group velocity result in a low lattice\nthermal conductivity of 0.62 W/mK at 300 K in consideration of four-phonon\nscattering. The current work not only provides a fundamental theoretical\ninsight into the thermal transport properties but also provides theoretical\nguidance for the practical thermal application of the BiAgOTe material.