Anharmonic, dimensionality and size effects in phonon transport

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Abstract
We have developed and employed a numerically efficient semi- ab initio theory, based on density-functional and relaxation-time schemes, to examine anharmonic, dimensionality and size effects in phonon transport in three- and two-dimensional solids of different crystal symmetries. Our method uses third- and fourth-order terms in crystal Hamiltonian expressed in terms of a temperature-dependent Grüneisen’s constant. All input to numerical calculations are generated from phonon calculations based on the density-functional perturbation theory. It is found that four-phonon processes make important and measurable contribution to lattice thermal resistivity above the Debye temperature. From our numerical results for bulk Si, bulk Ge, bulk MoS 2 and monolayer MoS 2 we find that the sample length dependence of phonon conductivity is significantly stronger in low-dimensional solids.
Funding Information
  • Leverhulme Trust (RPG-2016-186)

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