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Title: On the Nanoscale Structure of K xFe 2-yCh 2 (Ch = S, Se): A Neutron Pair Distribution Function View

Abstract

Comparative exploration of the nanometer-scale atomic structure of K xFe 2-yCh 2 (Ch = S, Se) was performed using neutron total scattering-based atomic pair distribution function (PDF) analysis of 5 K powder diffraction data in relation to physical properties. Whereas K xFe 2-ySe 2 is a superconductor with a transition temperature of about 32 K, the isostructural sulphide analogue is not, which instead displays a spin glass semiconducting behavior at low temperatures. The PDF analysis explores phase separated and disordered structural models as candidate descriptors of the low temperature data. For both materials, the nanoscale structure is well described by the iron (Fe)-vacancy-disordered K 2Fe 5-yCh 5 (I4/m) model containing excess Fe. An equally good description of the data is achieved by using a phase separated model comprised of I4/m vacancy-ordered and I4/mmm components. The I4/mmm component appears as a minority phase in the structure of both K xFe 2-ySe 2 and K xFe 2-yS 2, and with similar contribution, implying that the phase ratio is not a decisive factor influencing the lack of superconductivity in the latter. Comparison of structural parameters of the Fe-vacancy-disordered model indicates that the replacement of selenium (Se) by sulphur (S) results in an appreciablemore » reduction in the Fe-Ch interatomic distances and anion heights, while simultaneously increasing the irregularity of FeCh 4 tetrahedra, suggesting the more significant influence of these factors. Finally, structural features are also compared to the non-intercalated FeSe and FeS parent phases, providing further information for the discussion about the influence of the lattice degrees of freedom on the observed properties in layered iron chalcogenides.« less

Authors:
 [1];  [2];  [3];  [3];  [2];  [2]; ORCiD logo [1]
  1. Inst. of Electronic Structure and Laser (IESL), Foundation for Research and Technology- Hellas (FORTH), Vassilika Vouton, Heraklion (Greece)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Neutron Scattering Division
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1459171
Report Number(s):
BNL-206809-2018-JAAM
Journal ID: ISSN 2410-3896
Grant/Contract Number:  
SC0012704
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Condensed Matter
Additional Journal Information:
Journal Volume: 3; Journal Issue: 3; Journal ID: ISSN 2410-3896
Publisher:
MDPI
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; neutron pair distribution function (PDF); intercalated iron superconductors; anion height; tetrahedron regularity

Citation Formats

Mangelis, Panagiotis, Lei, Hechang, McDonnell, Marshall, Feygenson, Mikhail, Petrovic, Cedomir, Bozin, Emil, and Lappas, Alexandros. On the Nanoscale Structure of KxFe2-yCh2 (Ch = S, Se): A Neutron Pair Distribution Function View. United States: N. p., 2018. Web. doi:10.3390/condmat3030020.
Mangelis, Panagiotis, Lei, Hechang, McDonnell, Marshall, Feygenson, Mikhail, Petrovic, Cedomir, Bozin, Emil, & Lappas, Alexandros. On the Nanoscale Structure of KxFe2-yCh2 (Ch = S, Se): A Neutron Pair Distribution Function View. United States. doi:10.3390/condmat3030020.
Mangelis, Panagiotis, Lei, Hechang, McDonnell, Marshall, Feygenson, Mikhail, Petrovic, Cedomir, Bozin, Emil, and Lappas, Alexandros. Tue . "On the Nanoscale Structure of KxFe2-yCh2 (Ch = S, Se): A Neutron Pair Distribution Function View". United States. doi:10.3390/condmat3030020. https://www.osti.gov/servlets/purl/1459171.
@article{osti_1459171,
title = {On the Nanoscale Structure of KxFe2-yCh2 (Ch = S, Se): A Neutron Pair Distribution Function View},
author = {Mangelis, Panagiotis and Lei, Hechang and McDonnell, Marshall and Feygenson, Mikhail and Petrovic, Cedomir and Bozin, Emil and Lappas, Alexandros},
abstractNote = {Comparative exploration of the nanometer-scale atomic structure of KxFe2-yCh2 (Ch = S, Se) was performed using neutron total scattering-based atomic pair distribution function (PDF) analysis of 5 K powder diffraction data in relation to physical properties. Whereas KxFe2-ySe2 is a superconductor with a transition temperature of about 32 K, the isostructural sulphide analogue is not, which instead displays a spin glass semiconducting behavior at low temperatures. The PDF analysis explores phase separated and disordered structural models as candidate descriptors of the low temperature data. For both materials, the nanoscale structure is well described by the iron (Fe)-vacancy-disordered K2Fe5-yCh5 (I4/m) model containing excess Fe. An equally good description of the data is achieved by using a phase separated model comprised of I4/m vacancy-ordered and I4/mmm components. The I4/mmm component appears as a minority phase in the structure of both KxFe2-ySe2 and KxFe2-yS2, and with similar contribution, implying that the phase ratio is not a decisive factor influencing the lack of superconductivity in the latter. Comparison of structural parameters of the Fe-vacancy-disordered model indicates that the replacement of selenium (Se) by sulphur (S) results in an appreciable reduction in the Fe-Ch interatomic distances and anion heights, while simultaneously increasing the irregularity of FeCh4 tetrahedra, suggesting the more significant influence of these factors. Finally, structural features are also compared to the non-intercalated FeSe and FeS parent phases, providing further information for the discussion about the influence of the lattice degrees of freedom on the observed properties in layered iron chalcogenides.},
doi = {10.3390/condmat3030020},
journal = {Condensed Matter},
number = 3,
volume = 3,
place = {United States},
year = {Tue Jul 03 00:00:00 EDT 2018},
month = {Tue Jul 03 00:00:00 EDT 2018}
}

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Works referenced in this record:

Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides
journal, September 1976