NbFeSb is a promising thermoelectric material which according to experimental and theoretical studies exhibits a high power factor of up to 10 mW m −1 K −2 at room temperature and ZT of 1 at 1000 K. In all previous theoretical studies, κ latt is calculated using simplified models, which ignore structural defects. In this work, we calculate κ latt by solving the Boltzmann transport equation and subsequently including the contributions of grain boundaries, point defects and electron-phonon interaction. The results for κ latt and ZT are in excellent agreement with experimental measurements. In addition, we investigate theoretically the thermoelectric properties of TaFeSb. The material has recently been synthesised experimentally, thus confirming the theoretical hypothesis for its stability. This encourages a full-scale computation of its thermoelectric performance. Our results show that TaFeSb is indeed an excellent thermoelectric material which has a very high power factor of 16 mW m −1 K −2 at room temperature and ZT of 1.5 at 1000 K.

We present a nanoscale structural and density functional study of the Mn doped 3D topological insulator Bi2Te3. X-ray absorption near edge structure shows that Mn has valency of nominally 2+. Extended x-ray absorption fine structure spectroscopy in combination with electron energy loss spectroscopy (EELS) shows that Mn is a substitutional dopant of Bi and Te and also resides in the van der Waals gap between the quintuple layers of Bi2Te3. Combination of aberration-corrected scanning transmission electron microscopy and EELS shows that Mn substitution of Te occurs in film regions with increased Mn concentration. First-principles calculations show that the Mn dopants favor octahedral sites and are ferromagnetically coupled.

Recently, an emerging new class of cubic π-polymorphs are being pursued as cost-effective and relatively less toxic materials for thermoelectric, photovoltaic, and optoelectronic applications. Using density functional formalism and semiclassical Boltzmann transport theory, we have systematically studied the thermoelectric performance of π-polymorphs. Hybrid functional (HSE03) is employed to realize accurate energy bandgaps, which helps to predict more accurate thermoelectric properties. The thermodynamic stability is observed by binding energies and phonon dispersions. It is observed that the Seebeck coefficients (S) are decreasing and electrical conductivities (σ) are increasing with carrier concentration. However, thermal conductivities are showing decreasing trends which lead to ultimately increased ZT. π-GeSe shows a high power factor $16.50 mW/mK 2 among all π-polymorphs. The figure of merit, ZT value, of π-SnS, π-SnSe, π-GeS, and π-GeSe are found to be 0.83, 1.20, 1.28, and 1.63 with optimal carrier concentration at 800 K. The present work highlights the potential of newly discovered cubic π-polymorphs of chalcogenides for highly efficient thermoelectric materials.

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Previous first-principles calculations have failed to reproduce many of the key thermoelectric features of Fe 2 VAl, e.g. the maximum values of the Seebeck coefficient S and its asymmetry with respect to the chemical potential. Also, previous theoretical predictions suggested that the pseudo band gap of Fe 2 VAl switches from indirect to direct upon doping. In this work, we report first-principles calculations that correctly reproduce the experimentally measured thermoelectric properties of Fe 2 VAl. This is achieved by adding a larger Hubbard U term to V atoms than to Fe atoms and including a scissors operator afterwards. As a result, bulk Fe 2 VAl is modelled as a gapless semiconductor with maximum S values of 76 and −158 µV/K for p-and n-type, respectively, which agree well with the experimental measurements.