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First‐principles prediction of the high‐pressure phase transition and electronic structure of FeO: Implications for the chemistry of the lower mantle and core
Author(s) -
Sherman David M.,
Jansen Henri J. F.
Publication year - 1995
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 - 10.1029/94gl03010
Subject(s) - mantle (geology) , phase transition , electronic structure , discontinuity (linguistics) , transition metal , phase (matter) , metal , high pressure , inner core , condensed matter physics , materials science , chemistry , chemical physics , thermodynamics , geology , geophysics , physics , metallurgy , mathematical analysis , biochemistry , mathematics , organic chemistry , catalysis , composite material
Under shock‐wave compression, Fe 1−x O undergoes a transition to a dense metallic phase at pressures near 70 GPa. The geochemical significance of this transition has been unclear. Here, first‐principles electronic structure calculations (using the FLAPW method and GGA exchange‐correlation) show that the shock‐wave discontinuity of FeO results from a RB1 (rhombohedrally distorted NaCl structure) to B8 (NiAs structure) transition. The metallic nature of the FeO (B8) phase is argued to result from a breakdown of the Mott insulating condition, rather than an Fe(3d)‐O(2p) gap closure. As such, the metallization of FeO is probably not a basis for invoking oxygen in the Earth's core. The stability of FeO(B8) over FeO (RB1) at high pressure is comparable to the ideal ‐TΔS of mixing of FeO in (Mg,Fe)O at mantle temperatures. Consequently, it is uncertain if FeO(B8) is present as a separate phase in the Earth's interior.