The Structure of Ammonia Monohydrate Vb: Implications for the ammonia-water system

Condensed Matter lunchtime seminar

The Structure of Ammonia Monohydrate Vb: Implications for the ammonia-water system

  • Event time: 1:00pm
  • Event date: 18th April 2011
  • Speaker: Craig Wilson (Formerly School of Physics & Astronomy, University of Edinburgh)
  • Location: Room 2511,

Event details

The ammonia hydrates amongst the simplest materials to posses mixed (O-H...N) and N-H...O) hydrogen bonds. These bonds are of fundamental interest as models for proton transfer reactions which play a significant role in biological reactions. High pressure studies generate information on the density dependence of the bond geometry and thus provide stringent tests for our understanding of such bonds. In addition, the ammonia hydrates are minerals in the context of the outer solar system [1]. Their behaviour and properties are thus directly relevant to problems such as the origin of Uranus' and Neptune's magnetic fields and the formation models of large satellites such as Titan, Triton and similar bodies like Pluto.

Although the phase diagrams of the ammonia hydrates have been extensively studied – ammonia monohydrate has six high-pressure phases[2] – only a few structures have been solved[3-5]. We have now explored in depth the ambient temperature high pressure phase of ammonia monohydrate, AMH Vb, which has remained unsolved since its discovery over ten years ago. We will present the result of combined x-ray single crystal and neutron powder techniques.---

[1] Ref from HEM-C thesis jsl to find [2] J. Loveday,R. J. Nelmes, in Proceedings of the XVIIth AIRAPT Conference, Hawaii 1999, 1, 133 [3] J. S. Loveday, R. J. Nelmes, Physical Review Letters 1999, 83, 4329 [4] J. S. Loveday, R. J. Nelmes, High Pressure Research 2004, 24, 45 [5] A. D. Fortes, E. Suard, M. H. Lemée-Cailleau, C. J. Pickard, R. J. Needs, Journal of the American Chemical Society 2009, 131, 13508

This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..

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