Effects of thermal expansion and four-phonon interactions on the lattice thermal conductivity of the negative thermal expansion materialScF3

Abstract

This work systematically investigates the lattice dynamics and phonon thermal transport behavior of the typical negative thermal expansion (NTE) material, cubic ScF3. By incorporating thermal expansion, the discrepancy between theoretically predicted and experimentally observed lattice thermal conductivity (𝜅L) is resolved using self-consistent phonon theory, combined with the three- and four-phonon scattering. Our findings reveal that four-phonon interactions significantly increase the 𝜅L of ScF3, which contradicts the traditional intuitive impression that four-phonon interactions suppress thermal transport. This counterintuitive behavior is attributed to the hardening of two rotating phonon modes induced by quartic anharmonicity, suppressing anharmonic scattering and increasing the 𝜅L. Furthermore, we show that thermal expansion enhances anharmonic scattering in ScF3, leading to a decrease in 𝜅L. This suppression of 𝜅L becomes more pronounced at high pressures due to the significantly enhanced NTE behavior; for instance, the room-temperature 𝜅L of ScF3 is reduced by up to 59% at 0.6 GPa. Our work provides deeper insights into the effects of four-phonon interactions and thermal expansion on thermal transport properties.