Premium
The structure of iron under the conditions of the Earth's inner core
Author(s) -
Vočadlo Lidunka,
Brodholt John,
Alfè Dario,
Price Geoffrey D.,
Gillan Michael J.
Publication year - 1999
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/1999gl900214
Subject(s) - inner core , tetragonal crystal system , anisotropy , ab initio , crystal structure , materials science , core (optical fiber) , crystallography , earth (classical element) , phase (matter) , outer core , chemistry , physics , organic chemistry , quantum mechanics , composite material , mathematical physics
The inferred density of the solid inner core indicates that it is predominantly made of iron. In order to interpret the observed seismic anisotropy and understand the high pressure and temperature behaviour of the core, it is essential to establish the crystal structure of iron under core conditions. On the basis of extrapolated experimental data, a number of candidate structures for the high P/T iron phase have been proposed, namely, body‐centred cubic ( bcc ), body‐centred tetragonal ( bct ), hexagonal close‐packed ( hcp ), double‐hexagonal close‐packed ( dhcp ) and an orthorhombically distorted hcp polymorph (Matsui, 1993; Stixrude and Cohen, 1995; Boehler, 1993; Saxena et al., 1996; Andrault et al., 1997). Here we present the results of the first fully ab initio free energy calculations for all of these polymorphs of iron at core pressures and temperatures. Our results show that hcp ‐Fe is the most stable polymorph of iron under the conditions of the Earth's inner core.