Understanding Thermoelectric Properties from Density Functional Theory

Das, Asim and V, Kanchana (2014) Understanding Thermoelectric Properties from Density Functional Theory. Masters thesis, Indian Institute of Technology, Hyderabad.

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Abstract

The electronic band structure and transport properties of SrAgFCh (Ch = S, Se, Te) are studiedusing the first principle density functional theory and solving the Boltzmann transport equationwithin the constant relaxation time approximation. The complete structural optimisation is carried out to get the ground state properties of all the compounds. The calculated ground stateproperties agree quite well with available experiments. The electronic band structures are calculated by means of the full-potential linear augmented plane wave method, using the Tran-Blahamodified Becke-Johnson potential and the calculated band gaps are found to be in good agreement with the experiments aswell as with other theoretical reports. The spin-orbit coupling shows a significant change in lifting the band degeneracy. Assuming constant relaxation time approximation, the transport coefficients related to thermoelectric effect are calculated by solving Boltzmann equation as implemented in BoltzTraP code. The calculated thermoelectric properties such as thermopower andelectrical conductivity as functions of hole and electron concentrations shows these compoundsto be promising candidate for better thermoelectric applications. The thermopower is found todecrease as we move from S to Te, whereas the electrical conductivity is found to be increaseand we also found that the investigated compounds are good candidate for p-type doping along the a-axis direction. 5

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