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Title: Refinement of the crystal structure of the high-temperature phase G{sub 0} in (NH{sub 4}){sub 2}WO{sub 2}F{sub 4} (powder, X-ray, and neutron scattering)

Abstract

The (NH{sub 4}){sub 2}WO{sub 2}F{sub 4} compound undergoes a series of phase transitions: G{sub 0} {yields} 201, K {yields} G{sub 1} {yields} 160, and K {yields} G{sub 2}, with a significant change in entropy ({Delta}S{sub 1} {approx} Rln10 at the G{sub 0} {yields} G{sub 1} transition), which indicates significant orientational disordering in the G{sub 0} phase and the order-disorder type of the phase transition. X-ray diffraction is used to identify the crystal structure of the G{sub 0} phase as rhombohedral (sp. gr. Cmcm, Z = 4), determine the lattice parameters and the positions of all atoms (except hydrogen), and show that [WO{sub 2}F{sub 4}]{sup 2-} ions can form a superposition of dynamic and static orientational disorders in the anionic sublattice. A determination of the orientational position of [NH{sub 4}]{sup +} ions calls for the combined method of elastic and inelastic neutron scattering. Inelastic neutron scattering is used to determine the state of hindered rotation for ammonium ions in the G{sub 0} phase. Powder neutron diffraction shows that the orientational disorder of NH{sub 4} ions can adequately be described within the free-rotation approximation.

Authors:
 [1];  [2]; ;  [3];  [4]; ;  [5]
  1. Joint Institute for Nuclear Research, Frank Neutron Physics Laboratory (Russian Federation)
  2. Oak Ridge National Laboratory, Neutron Scattering Sciences Division (United States)
  3. Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation)
  4. Russian Academy of Sciences, Institute of Chemistry, Far Eastern Branch (Russian Federation)
  5. Russian Academy of Sciences, Kirensky Institute of Physics, Siberian Branch (Russian Federation)
Publication Date:
OSTI Identifier:
22156462
Resource Type:
Journal Article
Journal Name:
Crystallography Reports
Additional Journal Information:
Journal Volume: 58; Journal Issue: 1; Other Information: Copyright (c) 2013 Pleiades Publishing, Ltd.; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1063-7745
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; APPROXIMATIONS; ENTROPY; INELASTIC SCATTERING; IONS; LATTICE PARAMETERS; NEUTRON DIFFRACTION; NEUTRON REACTIONS; ORTHORHOMBIC LATTICES; PHASE TRANSFORMATIONS; POWDERS; ROTATION; TRIGONAL LATTICES; X RADIATION; X-RAY DIFFRACTION

Citation Formats

Novak, D. M., E-mail: dmn@nf.jinr.ru, Smirnov, L. S., Kolesnikov, A. I., Voronin, V. I., Berger, I. F., Laptash, N. M., Vasil'ev, A. D., and Flerov, I. N. Refinement of the crystal structure of the high-temperature phase G{sub 0} in (NH{sub 4}){sub 2}WO{sub 2}F{sub 4} (powder, X-ray, and neutron scattering). United States: N. p., 2013. Web. doi:10.1134/S1063774513010240.
Novak, D. M., E-mail: dmn@nf.jinr.ru, Smirnov, L. S., Kolesnikov, A. I., Voronin, V. I., Berger, I. F., Laptash, N. M., Vasil'ev, A. D., & Flerov, I. N. Refinement of the crystal structure of the high-temperature phase G{sub 0} in (NH{sub 4}){sub 2}WO{sub 2}F{sub 4} (powder, X-ray, and neutron scattering). United States. https://doi.org/10.1134/S1063774513010240
Novak, D. M., E-mail: dmn@nf.jinr.ru, Smirnov, L. S., Kolesnikov, A. I., Voronin, V. I., Berger, I. F., Laptash, N. M., Vasil'ev, A. D., and Flerov, I. N. 2013. "Refinement of the crystal structure of the high-temperature phase G{sub 0} in (NH{sub 4}){sub 2}WO{sub 2}F{sub 4} (powder, X-ray, and neutron scattering)". United States. https://doi.org/10.1134/S1063774513010240.
@article{osti_22156462,
title = {Refinement of the crystal structure of the high-temperature phase G{sub 0} in (NH{sub 4}){sub 2}WO{sub 2}F{sub 4} (powder, X-ray, and neutron scattering)},
author = {Novak, D. M., E-mail: dmn@nf.jinr.ru and Smirnov, L. S. and Kolesnikov, A. I. and Voronin, V. I. and Berger, I. F. and Laptash, N. M. and Vasil'ev, A. D. and Flerov, I. N.},
abstractNote = {The (NH{sub 4}){sub 2}WO{sub 2}F{sub 4} compound undergoes a series of phase transitions: G{sub 0} {yields} 201, K {yields} G{sub 1} {yields} 160, and K {yields} G{sub 2}, with a significant change in entropy ({Delta}S{sub 1} {approx} Rln10 at the G{sub 0} {yields} G{sub 1} transition), which indicates significant orientational disordering in the G{sub 0} phase and the order-disorder type of the phase transition. X-ray diffraction is used to identify the crystal structure of the G{sub 0} phase as rhombohedral (sp. gr. Cmcm, Z = 4), determine the lattice parameters and the positions of all atoms (except hydrogen), and show that [WO{sub 2}F{sub 4}]{sup 2-} ions can form a superposition of dynamic and static orientational disorders in the anionic sublattice. A determination of the orientational position of [NH{sub 4}]{sup +} ions calls for the combined method of elastic and inelastic neutron scattering. Inelastic neutron scattering is used to determine the state of hindered rotation for ammonium ions in the G{sub 0} phase. Powder neutron diffraction shows that the orientational disorder of NH{sub 4} ions can adequately be described within the free-rotation approximation.},
doi = {10.1134/S1063774513010240},
url = {https://www.osti.gov/biblio/22156462}, journal = {Crystallography Reports},
issn = {1063-7745},
number = 1,
volume = 58,
place = {United States},
year = {Tue Jan 15 00:00:00 EST 2013},
month = {Tue Jan 15 00:00:00 EST 2013}
}