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Structural disorder in (Bi,M)2(Fe,Mn,Bi)2O6+x (M = Na or K) pyrochlores seen from reverse Monte Carlo analysis of neutron total scattering
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Daniels, Luke M., Playford, Helen Y., Hannon, Alex C. and Walton, Richard I. (2017) Structural disorder in (Bi,M)2(Fe,Mn,Bi)2O6+x (M = Na or K) pyrochlores seen from reverse Monte Carlo analysis of neutron total scattering. Journal of Physical Chemistry C, 121 (33). pp. 18120-18128. doi:10.1021/acs.jpcc.7b04972 ISSN 1932-7447.
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Official URL: https://doi.org/10.1021/acs.jpcc.7b04972
Abstract
The average structures of the polycrystalline pyrochlores (Na0.60Bi1.40)(Fe1.06Mn0.17Bi0.77)O6.87 and (K0.24Bi1.51)(Fe1.07Mn0.15Bi0.78)O6.86 can be refined through Rietveld refinement against Bragg scattering data using cubic space group Fd3 ̅m, with off-centred 96h and 32e positions describing the A2Oʹ network. Investigation of their local structures through neutron total scattering confirms the extent of disorder within these materials, and furthermore shows significant deviation from the average structure, which is not accounted for through analysis of Bragg data alone. Reverse Monte Carlo (RMC) analysis with a 6 × 6 × 6 supercell was used to model accurately this local disorder, revealing ellipsoidal distributions for A-site potassium, distinctly different to the hollow torus-shaped distributions for the sodium and bismuth cations. It is shown through bond valence sum analysis that whilst these atomic displacements allow for the steric preferences of Bi3+, they are also necessary to satisfy the valence of both the bismuth and the alkali metals on the A sites. Analysis of the final RMC configuration showed the BO6 octahedra for the separate B site metals to be more regular (O–B–O ≈ 90°) than those in the Rietveld model (O–B–O ≈ 85/95°) which describes an average of the three different environments.
Item Type: | Journal Article | ||||||||||||||||||
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Subjects: | Q Science > QD Chemistry | ||||||||||||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Chemistry | ||||||||||||||||||
Library of Congress Subject Headings (LCSH): | Chemistry, Physical and theoretical, Monte Carlo method, Niobium | ||||||||||||||||||
Journal or Publication Title: | Journal of Physical Chemistry C | ||||||||||||||||||
Publisher: | American Chemical Society | ||||||||||||||||||
ISSN: | 1932-7447 | ||||||||||||||||||
Official Date: | 24 August 2017 | ||||||||||||||||||
Dates: |
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Volume: | 121 | ||||||||||||||||||
Number: | 33 | ||||||||||||||||||
Page Range: | pp. 18120-18128 | ||||||||||||||||||
DOI: | 10.1021/acs.jpcc.7b04972 | ||||||||||||||||||
Status: | Peer Reviewed | ||||||||||||||||||
Publication Status: | Published | ||||||||||||||||||
Access rights to Published version: | Restricted or Subscription Access | ||||||||||||||||||
Date of first compliant deposit: | 27 July 2017 | ||||||||||||||||||
Date of first compliant Open Access: | 26 July 2018 | ||||||||||||||||||
RIOXX Funder/Project Grant: |
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