• Stone, H. J.
• Fortes, A. D.
• Marshall, W. G.
• Dobson, David P.
• Cooper, Frances
• Wood, Ian G.
• Francis, D. J.
• Mccannon, C. A.
• Tucker, M. G.
• Walker, A. M.
• Vocadlo, Lidunka
• Neale, J. W.
• Price, G. David

Abstract

<p>The ability to perform neutron diffraction studies at simultaneous high pressures<br/> and high temperatures is a relatively recent development. The suitability of this<br/> technique for determining P–V–T equations of state has been investigated by<br/> measuring the lattice parameters of Mg_1-xFe_xO (x = 0.2, 0.3, 0.4), in the range<br/> P &lt; 10.3 GPa and 300 &lt; T &lt; 986 K, by time-of-flight neutron powder diffraction.<br/> Pressures were determined using metallic Fe as a marker and temperatures were<br/> measured by neutron absorption resonance radiography. Within the resolution<br/> of the experiment, no evidence was found for any change in the temperature<br/> derivative of the isothermal incompressibility, ∂KT/∂T, with composition. By<br/> assuming that the equation-of-state parameters either varied linearly or were<br/> invariant with composition, the 60 measured state points were fitted<br/> simultaneously to a P–V–T–x equation of state, leading to values of ∂KT/∂T =-0.024 (9) GPa K^-1 and of the isothermal Anderson–Grüneisen parameter ∂_T =<br/> 4.0 (16) at 300 K. Two designs of simultaneous high-P/T cell were employed<br/> during this study. It appears that, by virtue of its extended pressure range, a<br/> design using toroidal gaskets is more suitable for equation-of-state studies than<br/> is the system described by Le Godec, Dove, Francis, Kohn, Marshall, Pawley,<br/> Price, Redfern, Rhodes, Ross, Schofield, Schooneveld, Syfosse, Tucker &amp; Welch<br/> [Mineral. Mag. (2001), 65, 737–748].</p>

Topics

• impedance spectroscopy
• mineral
• experiment
• neutron diffraction