Ab initio Lattice Dynamics for Materials with Energy Applications

11:00 AM - 12:00 PM
Saikat Mukhopadhyay, Cornell University, Ithaca, New York
Materials Science and Technology Division Seminar
Chemical and Materials Sciences Building (4100), Room C-301
Email: David Singh

The quest for new materials with potential energy applications has attracted significant research interests in recent years and resulted in discoveries of many new materials for Li+ batteries and thermoelectric applications. However, mapping the relationship between the materials structures and their properties is indispensable for further developments in this field. Combining first principle lattice dynamics and experimental measurements, I plan to address three long standing issues on structures-properties relationship in these materials. (1) In the first part of the talk, I will demonstrate an easy and fast route to characterize the garnet type solid electrolytes which presently requires neutron diffraction and XRD, and therefore, is expensive and time-consuming. Since the performance of solid electrolytes critically depends on the level of dopants and vacancies, this will serve to substantially speed up the characterization of samples and their correlation to measured conductivity. (2) I will establish the relationship between the complex structure of higher manganese silicides (HMS) and their low thermal conductivity and reasonably high thermoelectric figure of merit. This immediately addresses the outstanding question on HMS-thermoelectrics concerning the origin of their anisotropic thermal conductivity. (3) Given that most of the promising thermoelectric materials are polar in nature and modulating their conductivity is one of the most efficient ways to enhance their thermoelectric properties, in the last part of my talk, I will provide conclusive evidence of polar effects on thermal conductivity in cubic boron nitride by using external pressure to change LO-TO splitting. This also leads to some intriguing implications for PbTe-thermoelectrics.


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