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Equation of state and phase transition of deuterated ammonia monohydrate (ND3 center dot D2O) measured by high-resolution neutron powder diffraction up to 500 MPa

Fortes, AD; Suard, E; Lemee-Cailleau, MH; Pickard, CJ; Needs, RJ; (2009) Equation of state and phase transition of deuterated ammonia monohydrate (ND3 center dot D2O) measured by high-resolution neutron powder diffraction up to 500 MPa. J CHEM PHYS , 131 (15) , Article 154503. 10.1063/1.3245858.

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Abstract

We describe the results of a neutron powder diffraction study of perdeuterated ammonia monohydrate (AMH, ND3 center dot D2O) carried out in the range 102 < P < 502 MPa at T = 180 K using the D2B high-resolution diffractometer at the Institut Laue-Langevin. This paper reports observations of the phase transformation from the low-pressure P2(1)2(1)2(1) phase (AMH I) to the high-pressure Pbca phase (AMH II) at 351 MPa, and measurements which have allowed us to determine the volumetric and axial incompressibilities of both polymorphs. At 180 K, the fitted third order Birch-Murnaghan equation of state of AMH I has parameters, V-0=248.00(2) angstrom(3), K-0=7.33(3) GPa with the first pressure derivative of K-0 fixed at the value obtained in ab initio calculations, (partial derivative K-0/partial derivative P)(T)=K-0'=5.3; the implied value of the second derivative is therefore (partial derivative K-2(0)/partial derivative P-2)(T)=K-0(n)=-0.94(1) GPa(-1). At 351 MPa, we observed that the transition from AMH I to AMH II occurred over a period of 90 min, with an associated reduction in molar volume of 4.6% and an increase in the incompressibility of 19.6%. (c) 2009 American Institute of Physics. [doi:10.1063/1.3245858]

Type:Article
Title:Equation of state and phase transition of deuterated ammonia monohydrate (ND3 center dot D2O) measured by high-resolution neutron powder diffraction up to 500 MPa
DOI:10.1063/1.3245858
Keywords:KINETIC INHIBITION, ICY SATELLITES, N-2 REDUCTION, SOLAR NEBULA, WATER SYSTEM, TITAN, DIHYDRATE, INTERIOR, ORIGIN, OCEAN
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Earth Sciences
UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Physics and Astronomy

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