Session G25 - Focus Session: Novel Thermoelectric Materials and Phenomena I.
FOCUS session, Tuesday morning, March 04
Room 16B, Austin Convention Center
Recent experiments have revealed that Si and Ge based crystalline clathrate materials have glass-like low lattice thermal conductivities. In this talk, I will summarize our recent theoretical investigation of lattice dynamics and thermal transport properties of materials of this class. Both accurate first-principles total energy method and efficient empirical molecular dynamics simulation techniques have been adopted in our study. The lattice thermal conductivity is directly evaluated through the heat current correlation functions based on the statistical linear response theory. The nano-open cage-like clathrate materials are examined in comparison with the conventional diamond-phase crystals and the fully tetrahedrally bonded amorphous solids. An interesting "oscillating" feature is found in the heat correlation functions of clathrate crystals, and this feature contributes a significant reduction in conductivity. Individual contributions from other effects, such as guest-rattlers, frame types, and Ga/Ge alloying, will be also be discussed. The predicted conductivities of Ge based materials are in good agreement with experiments.