Multiscale modeling of thermal transport and thermoelectric properties of defected nanostructures.

摘要

Thermal transport and thermoelectric properties of nanostructured materials have received much attention in recent years. Due to the reduced dimensionality and change in density of states, the thermal transport and thermoelectric properties of nanomaterials can be very unique and interesting as compared with their bulk counterparts. In order to better utilize nanomaterials, it is important to develop and apply computational models to design the material with desired transport properties. This dissertation focuses on the following topics:;1. We have investigated thermal transport properties of graphene with various defects, such as isotope, vacancy, and oxygen functional group. In the isotope effect study, we use the Green-Kubo method to compute thermal conductivity, and we developed a hybrid thermal transport model which applies long wavelength phonon correction to result from the Green-Kubo method. The simulation result is in good agreement with experiment data.;2. We studied thermoelectric properties of graphene using non-equilibrium Green function method. The electron transport across grain boundary in graphene is also investigated.;3. For thermoelectric materials Mg2Si, we developed empirical potential for Mg-Si alloy with modified embedded atom method, and the potential parameters were optimized against first principle data. We used non-equilibrium molecular dynamics simulation method to compute thermal conductivity of Mg 2Si with this developed potential.;4. Based on reactive force field method, we developed empirical potential for Li-Si compounds to model Si anode material for Li-ion battery application.