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Persistent URL http://purl.org/net/epubs/work/51154521
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Record Id 51154521
Title Experimental and computational studies of the structure, thermal expansion and volume isotope effect in high pressure ices.
Abstract Exploration by spacecraft of the outer solar system has revealed that the moons of the giant planets are geologically active worlds. Some could sup- port subsurface oceans, even life. Computer models have been designed to emulate the geological evolution of these moons but, to make useful predictions, reliable information about the likely layers of ice and rock within their interiors is needed. This thesis has investigated several high-pressure ice phases, namely ices II, III, V and VI, which could occur in the regime of pressure and temperature likely to exist in the mantle of an icy moon. Consequently, they are good candidates as ’rock forming’ materials and are likely to form icy shells surrounding a moon’s inner core. Samples of both D2O and H2O ices II, III, V and VI were manufactured in the laboratory by means of a piston-cylinder cell. Their high-pressure structures were preserved at ambient pressure by recovery and storage under liquid nitrogen. The samples were then investigated by neutron powder diffraction (at ambient pressure and temperatures from 10-150 K) using the High Resolution Powder Diffractometer (HRPD) at the ISIS facility in the UK, so as to accurately determine both their crystal structures and thermal expansion coefficients. All of these ice phases exhibit a ‘normal’ volume isotope effect, “VIE”, with V(H2O) > V(D2O). The effect of hydrogen ordering at low temperatures was also investigated and found to be isotope independent. To compliment the experimental work, ab initio simulations of ices II, IX and XI were made using density functional theory (DFT). These calculations broadly replicated the experimental values for thermal expansion and correctly predicted the VIE for ices II and III. However, for ice XI (an ordered form of ice Ih) a normal VIE was predicted below 130 K, in conflict with experimental results for ice Ih.
Organisation ISIS , ISIS-HRPD , STFC
Funding Information
Related Research Object(s): 10.5286/ISIS.E.82355015 , 10.5286/ISIS.E.84743199 , 10.5286/ISIS.E.87854424 , 10.5286/ISIS.E.89963299 , 10.5286/ISIS.E.90600061 , 10.5286/ISIS.E.RB1820294
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Language English (EN)
Type Details URI(s) Local file(s) Year
Thesis PhD, University College London, 2021. https://discovery…/id/eprint/10145115/ 2021