Phonon Conductivity Metrics for Compact, Linked-Cage, Layered, and Filled-Cage Crystals, Using Ab Initio, Molecular Dynamics and BoltzmannTransport Treatments

Thermal Conductivity;Structure Metrics;Bismuth Telluride;Skutterudite;Mechanical Engineering;Engineering;Mechanical Engineering

Huang, BaolingVan Der Ven, Anton ;

University of Michigan

关键词: Thermal Conductivity;    Structure Metrics;    Bismuth Telluride;    Skutterudite;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/61561/baolingh_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Atomic-level thermal transport in compact, layered, linked-cage, and filled-cagecrystals is investigated using a multiscale approach,combines the ab initio calculation, molecular dynamics (MD), Boltzman transport equations (BTE), and the kinetic theory. These materials are of great interests in energy storage, transport, and conversion. The structural metrics of phonon conductivity of these crystals are then explored.An atomic structure-based model is developed for the understanding the relationship between the atomic structure and phonon transport in compact crystals at hightemperatures. The elemental electronegativity, element mass, and the arrangementof bonds are found to be the dominant factors to determine the phonon conductivity.As an example of linked-cage crystals, the phonon conductivity of MOF-5 is investigate over a wide temperature range using MD simulations and the Green-Kubo method. The temperature dependence of the thermal conductivity of MOF-5 is found to be weak at high temperatures, which results from the suppression of the long-range acoustic phonon transport by the special linked-cage structure. The mean free path of the majority of phonons in MOF-5 is limited by the cage size. The phonon and electron transport in layered Bi2Te3 structure are investigated using the first-principle calculations, MD, and BTE. Strong anisotropy has been found for both phonon and electron transport due to the special layered structure. Temperature dependence of the energy gap and appropriatemodelling of relaxation times are found to be important for the prediction of the electrical transport in the intrinsic regime. The scattering by the acoustic, optical, and polar-optical phonons are found to dominate the electron transport. For filled skutterudite structure, strong coupling between the filler and the host is found. The interatomic bonds of the host are significantly affected by the filler. It is shown that without changing theinteratomic potentials for the host, the filler itself can not result in a lower phononconductivity for the filled structure. It is also found that the behavior of partially-filled skutterudites can be better understood by treating the partially-filled structureas a solid solution of the empty structure and fully-filled structure.