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:
-
- Joint Institute for Nuclear Research, Frank Neutron Physics Laboratory (Russian Federation)
- Oak Ridge National Laboratory, Neutron Scattering Sciences Division (United States)
- Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation)
- Russian Academy of Sciences, Institute of Chemistry, Far Eastern Branch (Russian Federation)
- 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}
}