Half-Heusler thermoelectric materials: NMR studies
Yefan Tian,Nader Ghassemi,Wuyang Ren,Wuyang Ren,Hangtian Zhu,Shan Li,Shan Li,Qian Zhang,Zhiming Wang,Zhifeng Ren,Joseph H. Ross +10 more
Reads0
Chats0
TLDR
In this paper, a series of half-Heusler semiconductors, including NbCoSn, ZrCoSb, TaFeSb and NbFeSsb, were used for nuclear magnetic resonance measurements and density functional theory (DFT) calculations.Abstract:
We report 59 Co, 93 Nb, and 121 Sb nuclear magnetic resonance measurements combined with density functional theory (DFT) calculations on a series of half-Heusler semiconductors, including NbCoSn, ZrCoSb, TaFeSb, and NbFeSb, to better understand their electronic properties and general composition-dependent trends. These materials are of interest as potentially high efficiency thermoelectric materials. Compared to the other materials, we find that ZrCoSb tends to have a relatively large amount of local disorder, apparently antisite defects. This contributes to a small excitation gap corresponding to an impurity band near the band edge. In NbCoSn and TaFeSb, Curie–Weiss-type behavior is revealed, which indicates a small density of interacting paramagnetic defects. Very large paramagnetic chemical shifts are observed associated with a Van Vleck mechanism due to closely spaced d bands splitting between the conduction and valence bands. Meanwhile, DFT methods were generally successful in reproducing the chemical shift trend for these half-Heusler materials, and we identify enhancement of the larger-magnitude shifts, which we connect to electron interaction effects. The general trend is connected to changes in d-electron hybridization across the series.read more
Citations
More filters
Journal ArticleDOI
Crystallographic design for half-Heuslers with low lattice thermal conductivity
TL;DR: In this article , the authors categorized low-κLattice thermal conductivity (κL) properties of half-heusler materials into three categories: heavy-element-containing, non-18-electron and quaternary double half-Heusler.
Metallic Shifts in NMR. A Review of the Theory and Comprehensive Critical Data Compilation of Metallic Materials. Part I. Review Chapters NMR Tables, Evaluated Knight Shifts in Metals Together with other Solid State and Nuclear Properties,
TL;DR: In this paper, critical evaluation methods and coverage are detailed in Chapter 8, and the evaluated Knight shift, together with many other physical properties that have been evaluated to a lesser extent, are treated in Chapter 9.
Journal ArticleDOI
Defect charging and resonant levels in half-Heusler Nb$_{1-x}$Ti$_x$FeSb
Yefan Tian,Farit G. Vagizov,Nader Ghassemi,Wuyang Ren,Hangtian Zhu,Zhiming Wang,Zhifeng Ren,Joseph H. Ross +7 more
TL;DR: In this paper, the NMR spin-lattice relaxation rate provides a measure of states within the valence band and the local paramagnetic susceptibility is significantly larger than expected based on DFT calculations, which discuss in terms of an enhancement of the susceptibility due to a Coulomb enhancement mechanism.
Journal Article
Achieving high power factor and output power density in p-type half-Heuslers Nb
Ran He,Daniel Kraemer,Jun Mao,Lingping Zeng,Qing Jie,Yucheng Lan,Chunhua Li,Jing Shuai,Hee Seok Kim,Yuan Liu,David Broido,Ching-Wu Chu,Gang Chen,Zhifeng Ren +13 more
TL;DR: In this paper, the authors achieved a peak power factor of ∼106 μW⋅cm−1⋆K−2 by increasing the hot pressing temperature up to 1,373 K in the p-type half-Heusler Nb0.95Ti0.05FeSb.
References
More filters
Journal ArticleDOI
Generalized Gradient Approximation Made Simple
TL;DR: A simple derivation of a simple GGA is presented, in which all parameters (other than those in LSD) are fundamental constants, and only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked.
Journal ArticleDOI
Double-slit photoelectron interference in strong-field ionization of the neon dimer.
Maksim Kunitski,Nicolas Eicke,Pia Huber,Jonas Köhler,S. Zeller,J. Voigtsberger,Nikolai Schlott,K. Henrichs,H. Sann,Florian Trinter,Lothar Ph. H. Schmidt,Anton Kalinin,Markus Schöffler,Till Jahnke,Manfred Lein,Reinhard Dörner +15 more
TL;DR: The authors show the double-slit interference effect in the strong-field ionization of neon dimers by employing COLTRIMS method to record the momentum distribution of the photoelectrons in the molecular frame.
Book
Principles of magnetic resonance
TL;DR: In this article, the effect of changing the precession frequency of the magnetic field has been studied using NMR to study rate properties. But the effect is limited to the case of double and double resonance.
Journal ArticleDOI
WIEN2k: An APW+lo program for calculating the properties of solids
Peter Blaha,Karlheinz Schwarz,Fabien Tran,Robert Laskowski,Georg K. H. Madsen,Laurence D. Marks +5 more
TL;DR: The WIEN2k program is based on the augmented plane wave plus local orbitals (APW+lo) method to solve the Kohn-Sham equations of density functional theory, and the various options, properties, and available approximations for the exchange-correlation functional are mentioned.