Plasticity in ammonia hydrates at high pressure and temperature
Water and ammonia are two of the main components of the mantle of the icy planets (Neptune, Uranus) and exoplanets. Modelling their interiors thus requires precise information on H2O/NH3 mixtures of various compositions over a large range of P-T conditions. The aim of this proposal is to probe the existence of a plastic phase, i.e. a crystalline phase where molecules can freely rotate around their lattice positions, in ammonia hemihydrate (AHH) by directly measuring the rotational dynamics of molecules. The existence of a plastic phase along melting curve at high temperature has been recently observed by our group in water and ammonia monohydrate by QENS and is predicted to occur at even milder conditions in AHH. We thus propose to perform HP-QENS measurements on AHH in the 1-10 GPa and 450 to 650 K range, at the IN5 time of flight using the Paris-Edinburgh pressure cell. This observation would be crucial for planetary sciences as plasticity strongly modifies the thermal and vibrational properties of the system, and is thought to promote the onset of superionicity, which is believed to be responsible for the anomalous magnetic field observed in Neptune-like icy bodies.
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The recommended format for citing this dataset in a research publication is in the following format:
s. ninet; BOVE Livia Eleonora; DATCHI Frédéric; R. Gaal; KACEM Nour Aicha; KLOTZ Stefan; KOZA Michael Marek; POREBA Tomasz and RESCIGNO Maria. (2023). Plasticity in ammonia hydrates at high pressure and temperature. Institut Laue-Langevin (ILL) doi:10.5291/ILL-DATA.7-02-215
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