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Interplay Between Electronic States and Structural Stability in Cation-Deficient VCoSb, NbCoSb, and TaCoSb Half-Heuslers

Title data

Miranda, Joaquin ; Gruhn, Thomas:
Interplay Between Electronic States and Structural Stability in Cation-Deficient VCoSb, NbCoSb, and TaCoSb Half-Heuslers.
In: Journal of Electronic Materials. Vol. 51 (2022) Issue 5 . - pp. 2043-2053.
ISSN 1543-186X
DOI: https://doi.org/10.1007/s11664-022-09510-0

Official URL: Volltext

Project information

Project financing: Deutsche Forschungsgemeinschaft

Abstract in another language

The effects of the vacancy concentration at the cation site of three half-Heuslers, VCoSb, NbCoSb, and TaCoSb, were studied with a combination of two computational methods: density functional theory and Monte Carlo simulations, both linked by a cluster expansion method. Our density functional method allows us to follow a gap opening in the electronic density of states in NbCoSb and TaCoSb as a function of vacancy concentration, starting from a metallic state with the Fermi-level crossing the valence states in the pristine crystal, passing throughout a p-type doped behavior, down to a semiconducting state at 20% of vacancies. In the case of VCoSb, the transition starts from the half-metallic ferromagnetic state, where VCoSb remains half-metallic until it achieves a semiconductor state at V$$_{0.8}$$CoSb composition, the transition leading to a magnetic–nonmagnetic crossover. Further increase of vacancies leads to non-polarized in-gap states in V$$_{0.75}$$CoSb, and polarized in-gaps in Nb$$_{0.77}$$CoSb, while Ta$$_{0.75}$$CoSb recovers a metallic behavior but with an n-character. Based on our cluster expansion, we can assert that Ta$$_{0.8}$$CoSb is slightly more stable than Nb$$_{0.8}$$CoSb, while both are much more stable than V$$_{0.8}$$CoSb. Temperature effects were studied through Monte Carlo simulations. The simulations show that, upon cooling, the ground states are hard to recover, and instead metastable states are formed. The vacancy arrangements were scrutinized with the help of suitable order parameters for the lattice vacancy occupation.

Further data

Item Type: Article in a journal
Refereed: Yes
Keywords: Defective half-Heuslers; vacancies; thermoelectrics; cluster expansion (CE); Monte Carlo; DFT; correlated disorder
Institutions of the University: Faculties > Faculty of Engineering Science > Chair Biomaterials > Chair Biomaterials - Univ.-Prof. Dr. Thomas Scheibel
Faculties > Faculty of Engineering Science
Faculties > Faculty of Engineering Science > Chair Biomaterials
Result of work at the UBT: Yes
DDC Subjects: 600 Technology, medicine, applied sciences > 620 Engineering
Date Deposited: 10 Sep 2022 21:00
Last Modified: 12 Sep 2022 05:42
URI: https://eref.uni-bayreuth.de/id/eprint/71788