Reports: AC10
44036-AC10 Intrinsic Lattice Thermal Conductivity of Nanostructured Semiconductor Systems
This research project is focused on the development of accurate theoretical approaches to calculate the lattice thermal conductivity, k, of bulk and nanotructured materials. During this reporting period, we have used our first principles approach to calculate k as a function of temperature for bulk silicon, germanium and diamond including both the intrinsic phonon-phonon scattering that arises from the anharmonicity of the interatomic forces and as well the isotopic impurity scattering. For all three cases, we obtain very good agreement with measured values for both highly enriched isotope concentrations and those occurring naturally. Since it involves no adustable input parameters, our first principles approach demonstrates potential to provide predictive capability to aid in the design of new materials for thermal management applications. We have also developed a theoretical description of the thermal conductivity of single-walled carbon nanotubes (SWCNTs). Our approach invokes for the first time the correct selection rules for three-phonon scattering and demonstrates the importance of anharmonic scattering of heat carrying acoustic phonons by optic phonons in correctly describing k for SWCNTs . We have also shown that the commonly used relaxation time approximation gives a poor description of thermal transport in SWCNTs because of the unusually weak phonon-phonon umklapp scattering.
