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Acoustic phonon softening leads to ultralow lattice thermal conductivity in monolayer Mg3SbBi
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杨
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蒋
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DOI：10.1016/j.commatsci.2026.114727.png)
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Abstract
En 中文
Knowledge of thermal transport is fundamental to the development of materials such as low thermal conductivity thermoelectrics, heat-resistant coatings, and refractories. In this work, the lattice thermal conductivity (kl), phonon, heat transport, and electric transport properties in monolayer Mg3SbBi are studied systematically by employing first-principles calculations coupled with the Boltzmann transport equation. The monolayer Mg3SbBi exhibits extremely low kl with 0.16 Wm−1 K−1 at 300 K compared to monolayer Mg3Sb2 with 1.2 Wm−1 K−1, which is attributed to the acoustic phonon softening in monolayer Mg3SbBi by substituting the lighter Sb atoms with the heavy Bi atom. The soft acoustic phonon modes primarily arise from the weakness of the ionic bonds (Mg2Sb, Mg3Sb, and Mg3Bi bonds), which reduces the phonon group velocity and enhances scattering, and thus leads to the lower kl. Besides, the maximum thermoelectric figures of merit (ZTmax) of n-type monolayer Mg3SbBi at 800 K is 0.21, which is higher than that of the similar binary monolayer Mg3Sb2 and Mg3Bi2. The study unveils that soft phonon modes can be constructed by tailoring chemical bonds to decrease kl, which provides critical guidance for searching for high-performance advanced thermoelectric and novel low thermal conductivity materials.
Keywords:
lattice thermal conductivity
phonon softening
thermoelectric materials
first-principles calculations
monolayer Mg3SbBi
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3.6W
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