Journal
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Volume 21, Issue 47, Pages 26033-26040Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c9cp05246a
Keywords
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Funding
- MOE tier 1 funding of NUS Faculty of Science, Singapore [R-144-000-402-114]
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We study the lattice thermal conductivity of two-dimensional (2D) pentagonal systems, such as penta-silicene and penta-germanene. Penta-silicene has been recently reported, while the stable penta-germanene, made up of another group IV element, is first revealed by our ab initio calculations. We find that both penta-silicene and penta-germanene at room temperature have ultra-low lattice thermal conductivities, kappa, of 1.29 W m(-1) K-1 and 0.30 W m(-1) K-1, respectively. To the best of our knowledge, penta-germanene may have the lowest kappa in 2D crystal materials. We attribute the ultra-low kappa to the weak phonon harmonic interaction and strong anharmonic scattering. A small phonon group velocity, a small Debye frequency, a large Gruneisen parameter, and a large number of modes available for phonon-phonon interplay together lead to the ultra-low kappa of penta-silicene and penta-germanene. These discoveries provide new insight into the manipulation of ultra-low kappa in 2D materials and highlight the potential applications of silicon and germanium based high thermoelectric materials.
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