Structure of vacancy-ordered single-crystalline superconducting potassium iron selenide

Zavalij, P. and Bao, W. and Wang, X.F. and Ying, J.J. and Chen, X.H. and Wang, D.M. and He, J.B. and Wang, X.Q. and Chen, G.F. and Hsieh, P.-Y. and Huang, Q. and Green, M.A. (2011) Structure of vacancy-ordered single-crystalline superconducting potassium iron selenide. Physical Review B - Condensed Matter and Materials Physics, 83 (13). p. 132509. ISSN 1098-0121. (doi:https://doi.org/10.1103/PhysRevB.83.132509) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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Official URL
http://dx.doi.org/10.1103/PhysRevB.83.132509

Abstract

With single-crystal x-ray diffraction studies, we compare the structures of three samples showing optimal superconductivity: K0.775(4)Fe 1.613(1)Se2, K0.737(6)Fe 1.631(3)Se2, and Cs0.748(2)Fe 1.626(1)Se2. All have an almost identical ordered vacancy structure with a (?5 × ?5 × 1) supercell. The tetragonal unit cell, space group I4/m, possesses lattice parameters at 250 K of a = b = 8.729(2) Å and c = 14.120(3) Å, a = b = 8.7186(12) Å and c = 14.0853(19) Å, and at 295 K, a = b = 8.8617(16) Å and c = 15.304(3) Å for the three crystals, respectively. The structure contains two iron sites; one is almost completely empty while the other is fully occupied. There are similarly two alkali metal sites that are occupied in the range of 72.2(2)%-85.3(3)%. The inclusion of alkali metals and the presence of vacancies within the structure allows for considerable relaxation of the FeSe4 tetrahedron, compared with members of the Fe(Te, Se, S) series, and the resulting shift of the Se-Fe-Se bond angles to less distorted geometry could be important in understanding the associated increase in the superconducting transition temperature. The structure of these superconductors are distinguished from the structure of the nonsuperconducting phases by an almost complete absence of Fe on the (0 0.5 0.25) site, as well as lower alkali metal occupancy that ensures an exact Fe2+ oxidation state, which are clearly critical parameters in the promotion of superconductivity. © 2011 American Physical Society.

Item Type: Article
Additional information: Unmapped bibliographic data: C7 - 132509 [EPrints field already has value set] LA - English [Field not mapped to EPrints] J2 - Phys. Rev. B Condens. Matter Mater. Phys. [Field not mapped to EPrints] AD - Department of Chemistry, University of Maryland, College Park, MD 20742, United States [Field not mapped to EPrints] AD - Department of Physics, Renmin University of China, Beijing 100872, China [Field not mapped to EPrints] AD - Hefei National Laboratory for Physical Science at Microscale, Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China [Field not mapped to EPrints] AD - Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, United States [Field not mapped to EPrints] AD - National Institute of Standards and Technology, Center for Neutron Research, 100 Bureau Dr., Gaithersburg, MD 20878, United States [Field not mapped to EPrints] DB - Scopus [Field not mapped to EPrints]
Subjects: Q Science > QC Physics > QC173.45 Condensed Matter
Q Science > QD Chemistry > QD478 Solid State Chemistry
Divisions: Faculties > Sciences > School of Physical Sciences > Functional Materials Group
Depositing User: Giles Tarver
Date Deposited: 14 Oct 2015 11:06 UTC
Last Modified: 21 Oct 2015 14:20 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/50978 (The current URI for this page, for reference purposes)
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