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The high-pressure phase diagram of ammonia dihydrate

Fortes, AD; Wood, IG; Alfredsson, M; Vocadlo, L; Knight, KS; Marshall, WG; ... Fernandez-Alonso, F; + view all (2007) The high-pressure phase diagram of ammonia dihydrate. HIGH PRESSURE RES , 27 (2) 201 - 212. 10.1080/08957950701265029.

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Abstract

We have investigated the P-T phase diagram of ammonia dihydrate (ADH), ND3 center dot 2D(2)O, using powder neutron diffraction methods over the range 0-9 GPa, 170-300 K. In addition to the ambient pressure phase, ADH I, we have identified three high-pressure phases, ADH II, III, and IV, each of which has been reproduced in at least three separate experiments. Another, apparently body-centred-cubic, phase of ADH has been observed on a single occasion above 6 GPa at 170 K. The existence of a dehydration boundary has been confirmed where, upon compression or warming, ADH IV decomposes to a high-pressure ice phase (ice VII or VIII) and a high-pressure phase of ammonia monohydrate (AMH V or VI).

Type:Article
Title:The high-pressure phase diagram of ammonia dihydrate
DOI:10.1080/08957950701265029
Keywords:ammonia dihydrate, neutron diffraction, polymorphism, ICY SATELLITES, POWDER DIFFRACTION, LIQUID, LEAD, EQUATION, SYSTEM, STATE
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Earth Sciences

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