How lewis acidity of the cationic framework affects KNaNbOF5 polymorphism

Kelvin B. Chang, Anastasiya Vinokur, Rachelle Ann F Pinlac, Matthew R. Suchomel, Michael R. Marvel, Kenneth R. Poeppelmeier

Research output: Contribution to journalArticle

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Abstract

The valence matching principle is used to explain the loss of inversion symmetry in the noncentrosymmetric (NCS) polymorph of KNaNbOF5 in comparison to its centrosymmetric (CS) polymorph. The [NbOF5] 2- anion has five contacts to both potassium and sodium in the NCS polymorph, whereas in the CS polymorph there are only four contacts to potassium and six contacts to sodium. The lower average Lewis acidity of the cationic framework in the NCS polymorph relative to the CS polymorph reflects the loss of inversion symmetry. This lower average Lewis acidity is achieved during hydrothermal synthesis with a potassium-rich solution when the K:Na ratio in the reaction is greater than 1:1, as the Lewis acidity of potassium is lower than that of sodium. The contrasting coordination environments are manifested in secondary distortions that weaken the primary Nb = O interaction and lengthen the Nb = O bond in the NCS polymorph. An unusual heat-induced phase transition from the CS to the NCS polymorph was studied with in situ powder X-ray diffraction. The transition to the NCS polymorph upon cooling occurs through an intermediate phase(s).

Original languageEnglish
Pages (from-to)6979-6984
Number of pages6
JournalInorganic Chemistry
Volume53
Issue number13
DOIs
Publication statusPublished - Jul 7 2014

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polymorphism
Polymorphism
Acidity
acidity
potassium
sodium
Potassium
inversions
symmetry
Sodium
anions
valence
cooling
heat
synthesis
Hydrothermal synthesis
diffraction
X ray powder diffraction
x rays
Anions

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry

Cite this

Chang, K. B., Vinokur, A., Pinlac, R. A. F., Suchomel, M. R., Marvel, M. R., & Poeppelmeier, K. R. (2014). How lewis acidity of the cationic framework affects KNaNbOF5 polymorphism. Inorganic Chemistry, 53(13), 6979-6984. https://doi.org/10.1021/ic500922s

How lewis acidity of the cationic framework affects KNaNbOF5 polymorphism. / Chang, Kelvin B.; Vinokur, Anastasiya; Pinlac, Rachelle Ann F; Suchomel, Matthew R.; Marvel, Michael R.; Poeppelmeier, Kenneth R.

In: Inorganic Chemistry, Vol. 53, No. 13, 07.07.2014, p. 6979-6984.

Research output: Contribution to journalArticle

Chang, KB, Vinokur, A, Pinlac, RAF, Suchomel, MR, Marvel, MR & Poeppelmeier, KR 2014, 'How lewis acidity of the cationic framework affects KNaNbOF5 polymorphism', Inorganic Chemistry, vol. 53, no. 13, pp. 6979-6984. https://doi.org/10.1021/ic500922s
Chang, Kelvin B. ; Vinokur, Anastasiya ; Pinlac, Rachelle Ann F ; Suchomel, Matthew R. ; Marvel, Michael R. ; Poeppelmeier, Kenneth R. / How lewis acidity of the cationic framework affects KNaNbOF5 polymorphism. In: Inorganic Chemistry. 2014 ; Vol. 53, No. 13. pp. 6979-6984.
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