Covalent bonding and the nature of band gaps in some half-Heusler compounds
TLDR
In this paper, the authors report a systematic examination of band gaps and the nature (covalent or ionic) of bonding in semiconducting 8 and 18-electron half-Heusler compounds through first-principles density functional calculations.Abstract:
Half-Heusler compounds XYZ, also called semi-Heusler compounds, crystallize in the C1b MgAgAs structure, in the space group . We report a systematic examination of band gaps and the nature (covalent or ionic) of bonding in semiconducting 8- and 18-electron half-Heusler compounds through first-principles density functional calculations. We find that the most appropriate description of these compounds from the viewpoint of electronic structures is one of a YZ zinc blende lattice stuffed by the X ion. Simple valence rules are obeyed for bonding in the 8-electron compound. For example, LiMgN can be written Li+ + (MgN)− and (MgN)−, which is isoelectronic with (SiSi), forms a zinc blende lattice. The 18-electron compounds can similarly be considered as obeying valence rules. A semiconductor such as TiCoSb can be written Ti4+ + (CoSb)4−; the latter unit is isoelectronic and isostructural with zinc-blende GaSb. For both the 8- and the 18-electron compounds, when X is fixed as some electropositive cation, the computed band gap varies approximately as the difference in Pauling electronegativities of Y and Z. What is particularly exciting is that this simple idea of a covalently bonded YZ lattice can also be extended to the very important magnetic half-Heusler phases; we describe these as valence compounds, i.e. possessing a band gap at the Fermi energy albeit only in one spin direction. The local moment in these magnetic compounds resides on the X site.read more
Citations
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Tunable multifunctional topological insulators in ternary Heusler compounds
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TL;DR: In this paper, it was shown that around 50 Heusler compounds show band inversion similar to that of HgTe, and the topological state in these zero-gap semiconductors can be created by applying strain or by designing an appropriate quantum-well structure, similar to the case of hgTe. The properties can open new research directions in realizing the quantized anomalous Hall effect and topological superconductors.
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Half-Heusler ternary compounds as new multifunctional experimental platforms for topological quantum phenomena
Hsin Lin,L. Andrew Wray,Yuqi Xia,Su-Yang Xu,Shuang Jia,Robert J. Cava,Arun Bansil,M. Zahid Hasan +7 more
TL;DR: The results suggest that half-Heuslers provide a new platform for deriving a host of topologically exotic compounds and their nanoscale or thin-film device versions through the inherent flexibility of their lattice parameter, spin-orbit strength and magnetic moment tunability paving the way for the realization of multifunctional topological devices.
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Evaluation of Half‐Heusler Compounds as Thermoelectric Materials Based on the Calculated Electrical Transport Properties
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