Strain-Driven Anomalous Lattice Thermal Conductivity in BaPdS₂

Strain engineering is one of the most promising and effective routes toward continuously turning the electronic and optical properties of materials, while thermal property is generally believed to be sensitive and positive with the mechanical compress strain. In this paper, we investigated the lattice thermal conductivity of zigzag chain-like wrinkled structure BaPdS₂ with uniaxial compress strain along <i>c</i>-axis based on first-principles calculations and phonon Boltzmann transport equation. Unlike the commonly belief that the lattice thermal conductivity increases (or decrease) with compress (or tensile) strain for bulk materials, it is found that the <i>κ_latt</i>-<i>c</i> was nearly unchanged and <i>κ_latt</i>-<i>a</i> was increased exceptionally for BaPdS₂ with strain imposed in <i>c</i>-axis. The unusual strain dependence thermal conductivity in <i>c</i>-axis was mainly attributed to the enhanced phonon phase space that neutralized the weakened anharmonicity and the enhanced group velocity. While the abnormal increased <i>κ_latt</i>-<i>a</i> is attributed to the weak anharmonicity with compress strain perpendicular to <i>a</i>-axis, equivalent to uniform biaxial tension strain in <i>ab</i> plane. In addition, high thermal conductivity anisotropy was observed because of the large group velocity disparity along <i>a</i>- and <i>c</i>-axis. The finding discovers materials with unusual thermal conduction mechanism under strain along different directions, as well as provides new material platforms for potential heat-routing or heat-managing devices.