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Summary: GEOPHYSICAL RESEARCH LETTERS, VOL. 27, NO. 16, PAGES 2417-2420, AUGUST 15, 2000
Thermodynamic stability of Fe/O solid solution at
inner-core conditions
D. Alf`e, G. D. Price
Research School of Geological and Geophysical Sciences Birkbeck College and University College London
Gower Street, London WC1E 6BT, UK.
M. J. Gillan
Physics and Astronomy Department, University College London Gower Street, London WC1E 6BT, UK.
Abstract. We present a new technique which allows the
fully ab initio calculation of the chemical potential of a sub-
stitutional impurity in a high-temperature crystal, including
harmonic and anharmonic lattice vibrations. The technique
uses the combination of thermodynamic integration and ref-
erence models developed recently for the ab initio calcula-
tion of the free energy of liquids and anharmonic solids. We
apply the technique to the case of the substitutional oxy-
gen impurity in h.c.p. iron under Earth's core conditions,
which earlier static ab initio calculations indicated to be
thermodynamically very unstable. Our results show that
entropic effects arising from the large vibrational amplitude
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