eprintid: 421 rev_number: 5 eprint_status: archive userid: 1 dir: disk0/00/00/04/21 datestamp: 2005-05-05 12:00:00 lastmod: 2015-07-23 09:33:08 status_changed: 2008-01-09 13:17:24 type: book_section metadata_visibility: show creators_name: Price, G.D. creators_name: Alfè, D. creators_name: Vočadlo, L. creators_name: Gillan, M.J. creators_id: GDPRI11 title: The earth’s core: an approach from first principles ispublished: pub subjects: 11000 subjects: 10600 divisions: F60 divisions: F57 note: An edited version of this paper was published by AGU. Copyright 2004 American Geophysical Union. abstract: The Earth’s core is largely composed of iron (Fe), alloyed with less dense elements such as sulphur, silicon and/or oxygen. The phase relations and physical properties of both solid and liquid Fe-alloys are therefore of great geophysical importance. As a result, over the past fifty years the properties of Fe and its alloys have been extensively studied experimentally. However, achieving the extreme pressures (up to 360 GPa) and temperatures (~6000K) found in the core provide a major experimental challenge, and it is not surprising that there are still considerable discrepancies in the results obtained by using different experimental techniques. In the past fifteen years quantum mechanical techniques have been applied to predict the properties of Fe. Here we review the progress that has been made in the use of first principles methods to study Fe and its alloys, and as a result of these studies we conclude: (i) that pure Fe adopts an hexagonal close packed structure under core conditions and melts at ~6200 K at 360 GPa, (ii) that thermodynamic equilibrium and observed seismic data are satisfied by a liquid Fe alloy outer core with a composition of ~10 mole% S (or Si) and 8 mole% O crystallising at ~ 5500 K to give an Fe alloy inner core with ~8 mole% S (or Si) and 0.2 mole % O, and (iii) that with such concentrations of S (or Si), an Fe alloy might adopt a body centred cubic structure in all or part of the inner core. In the future the roles of Ni, C, H and K in the core need to be studied, and techniques to predict the transport and rheological properties of Fe alloys need to be developed. date: 2004 date_type: published publisher: American Geophysical Union official_url: http://www.agu.org/ vfaculties: VMPS vfaculties: VMPS oa_status: green language: eng primo: open primo_central: open_green lyricists_name: Price, G lyricists_id: GDPRI11 full_text_status: public series: Geophysical Monograph Series number: 150 pagerange: 1-12 refereed: TRUE isbn: 0875904157 book_title: The state of the planet: frontiers and challenges in geophysics editors_name: Sparks, R.S.J. editors_name: Hawksworth, C.J. citation: Price, G.D.; Alfè, D.; Vočadlo, L.; Gillan, M.J.; (2004) The earth’s core: an approach from first principles. In: Sparks, R.S.J. and Hawksworth, C.J., (eds.) The state of the planet: frontiers and challenges in geophysics. (pp. 1-12). American Geophysical Union Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/421/1/IUGG2003.pdf