Octahedral tilting in the polar hexagonal tungsten bronzes RbNbW2O9 and KNbW2O9

Jason A. McNulty; Alexandra Gibbs; Philip Lightfoot; Finlay D. Morrison

doi:10.1107/S2052520619009260

Octahedral tilting in the polar hexagonal tungsten bronzes RbNbW₂O₉ and KNbW₂O₉

Jason A. McNulty, Alexandra Gibbs, Philip Lightfoot, Finlay D. Morrison

Research output: Contribution to journal › Article › peer-review

Abstract

The ambient temperature structures (orthorhombic, space group, Cmc2₁) of the polar hexagonal tungsten bronzes RbNbW₂O₉ and KNbW₂O₉ have been determined by high-resolution powder neutron diffraction. Displacement of the A-site cation in the polar c-axis, with concomitant octahedral tilting, occurs to optimise the A-cation bonding environment reducing the coordination from 18 to 16. This effect is more evident in KNbW₂O₉ due to decreased A-cation size. The octahedral tilting in both compositions results in a doubling of the c-axis that has not previously been reported, highlighting the importance of neutron diffraction as a complementary technique for structural determination of such systems.

Original language	English
Article number	B75
Number of pages	7
Journal	Acta Crystallographica. Section B, Structural Science
Volume	75
Issue number	Part 5
Early online date	7 Sept 2019
DOIs	https://doi.org/10.1107/S2052520619009260
Publication status	Published - Oct 2019

Keywords

Octahedral tilting
Polar bears
Hexagonal tungsten bronzes
Powder neutron diffraction
Symmetry mode analysis.

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New Horizon in Nanoscale: Ferrolectric, Ferroelastic and Multiferroic Domain Walls: a New Horizon in Nanoscale Functional Materials
Scott, J. F. (PI) & Morrison, F. (CoI)
EPSRC
1/04/17 → 31/03/21
Project: Standard

Data relating to article "Octahedral Tilting in the Polar Hexagonal Tungsten Bronzes RbNbW2O9 and KNbW2O9"
McNulty, J. A. (Creator), Gibbs, A. (Contributor), Lightfoot, P. (Contributor) & Morrison, F. D. (Contributor), University of St Andrews, 2019
DOI: 10.17630/17fd26d7-6099-4685-9762-f1a65b1e2d4e
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title = "Octahedral tilting in the polar hexagonal tungsten bronzes RbNbW2O9 and KNbW2O9",

abstract = "The ambient temperature structures (orthorhombic, space group, Cmc21) of the polar hexagonal tungsten bronzes RbNbW2O9 and KNbW2O9 have been determined by high-resolution powder neutron diffraction. Displacement of the A-site cation in the polar c-axis, with concomitant octahedral tilting, occurs to optimise the A-cation bonding environment reducing the coordination from 18 to 16. This effect is more evident in KNbW2O9 due to decreased A-cation size. The octahedral tilting in both compositions results in a doubling of the c-axis that has not previously been reported, highlighting the importance of neutron diffraction as a complementary technique for structural determination of such systems.",

keywords = "Octahedral tilting, Polar bears, Hexagonal tungsten bronzes, Powder neutron diffraction, Symmetry mode analysis.",

author = "McNulty, {Jason A.} and Alexandra Gibbs and Philip Lightfoot and Morrison, {Finlay D.}",

note = "We thank the Science and Technology Facilities Council (STFC) for the provision of neutron diffraction facilities at ISIS (HRPD experiment RB1710021, doi: 10.5286/ISIS.E.RB1710021) and the School of Chemistry, University of St Andrews for funding of a studentship to JAM through the EPSRC doctoral training grant (EP/K503162/1).",

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AU - Gibbs, Alexandra

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AU - Morrison, Finlay D.

N1 - We thank the Science and Technology Facilities Council (STFC) for the provision of neutron diffraction facilities at ISIS (HRPD experiment RB1710021, doi: 10.5286/ISIS.E.RB1710021) and the School of Chemistry, University of St Andrews for funding of a studentship to JAM through the EPSRC doctoral training grant (EP/K503162/1).

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N2 - The ambient temperature structures (orthorhombic, space group, Cmc21) of the polar hexagonal tungsten bronzes RbNbW2O9 and KNbW2O9 have been determined by high-resolution powder neutron diffraction. Displacement of the A-site cation in the polar c-axis, with concomitant octahedral tilting, occurs to optimise the A-cation bonding environment reducing the coordination from 18 to 16. This effect is more evident in KNbW2O9 due to decreased A-cation size. The octahedral tilting in both compositions results in a doubling of the c-axis that has not previously been reported, highlighting the importance of neutron diffraction as a complementary technique for structural determination of such systems.

AB - The ambient temperature structures (orthorhombic, space group, Cmc21) of the polar hexagonal tungsten bronzes RbNbW2O9 and KNbW2O9 have been determined by high-resolution powder neutron diffraction. Displacement of the A-site cation in the polar c-axis, with concomitant octahedral tilting, occurs to optimise the A-cation bonding environment reducing the coordination from 18 to 16. This effect is more evident in KNbW2O9 due to decreased A-cation size. The octahedral tilting in both compositions results in a doubling of the c-axis that has not previously been reported, highlighting the importance of neutron diffraction as a complementary technique for structural determination of such systems.

KW - Octahedral tilting

KW - Polar bears

KW - Hexagonal tungsten bronzes

KW - Powder neutron diffraction

KW - Symmetry mode analysis.

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JO - Acta Crystallographica. Section B, Structural Science

JF - Acta Crystallographica. Section B, Structural Science

IS - Part 5

M1 - B75

ER -

Octahedral tilting in the polar hexagonal tungsten bronzes RbNbW2O9 and KNbW2O9

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Keywords

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New Horizon in Nanoscale: Ferrolectric, Ferroelastic and Multiferroic Domain Walls: a New Horizon in Nanoscale Functional Materials

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Cite this

Octahedral tilting in the polar hexagonal tungsten bronzes RbNbW₂O₉ and KNbW₂O₉