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Your search keyword '"C. W. Wilson"' showing total 4 results
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4 results on '"C. W. Wilson"'

1. Topologically frustrated ionisation in a water-ammonia ice mixture

Author

C. Liu, A. Mafety, J. A. Queyroux, C. W. Wilson, H. Zhang, K. Béneut, G. Le Marchand, B. Baptiste, P. Dumas, G. Garbarino, F. Finocchi, J. S. Loveday, F. Pietrucci, A. M. Saitta, F. Datchi, and S. Ninet

Subjects
Science
Abstract

Water and ammonia are major constituents of icy planet interiors, however their phase behaviour under extreme conditions remain relatively unknown. Here, the authors show that ammonia monohydrate transforms under pressure into an alloy composed of molecules as well as ions, owing to a topological frustration.

Published
2017
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3. On the stability of the disordered molecular alloy phase of ammonia hemihydrate

Author

D. M. Amos, C. W. Wilson, Craig L. Bull, Mary-Ellen Donnelly, G. W. Stinton, and John Loveday

Subjects
MONOHYDRATE, MODELS, Inorganic chemistry, Alloy, General Physics and Astronomy, Crystal structure, DIAGRAM, engineering.material, NEUTRON POWDER DIFFRACTION, Pressure range, Ammonia, chemistry.chemical_compound, HIGH-PRESSURE, Physical and Theoretical Chemistry, Phase diagram, Hydrogen compounds, Hemihydrate, GPA, Ammonium compounds, chemistry, PARIS-EDINBURGH CELL, engineering, Physical chemistry, COMPRESSION, DIHYDRATE, SYSTEM
Abstract

The disordered-molecular-alloy phase (DMA) of ammonia hydrates [J.S. Loveday and R. J. Nelmes, Phys. Rev. Lett. 83, 4329 (1999)] is unique in that it has substitutional disorder of ammonia and water over the molecular sites of a body centred cubic lattice. Whilst this structure has been observed in ammonia di- and mono-hydrate compositions, it has not been conclusively observed in the ammonia hemihydrate system. This work presents investigations of the structural behaviour of ammonia hemihydrate as a function of P and T. The indications of earlier studies [Ma et al. RSC Adv. 2, 4290 (2012)] that the DMA structure could be produced by compression of ammonia hemihydrate above 20 GPa at ambient temperature are confirmed. In addition, the DMA structure was found to form reversibly both from the melt, and on warming of ammonia hemihydrate phase-II, in the pressure range between 4 and 8 GPa. The route used to make the DMA structure from ammonia mono-and di-hydrates-compression at 170 K to 6 GPa followed by warming to ambient temperature-was found not to produce the DMA structure for ammonia hemihydrate. These results provide the first strong evidence that DMA is a thermodynamically stable form. A high-pressure phase diagram for ammonia hemihydrate is proposed which has importance for planetary modelling. (C) 2015 AIP Publishing LLC.

Published
2015
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