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The nature of the pressure‐induced metallization of FeO and its implications to the core‐mantle boundary
Author(s) -
Sherman David M.
Publication year - 1989
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/gl016i006p00515
Subject(s) - antiferromagnetism , spins , condensed matter physics , mantle (geology) , néel temperature , electron , materials science , high pressure , transition metal , metal , ambient pressure , geology , chemistry , thermodynamics , metallurgy , physics , magnetic field , geophysics , biochemistry , magnetization , quantum mechanics , catalysis
The pressure and temperature‐induced metallization of FeO discovered by Knittle et al [1986] is here argued to result from a Mott transition associated with increased Fe(3d)‐Fe(3d) orbital overlap at high pressures. The metallic bonding in the Fe(3d) t 2g band may account for the 4% volume decrease of FeO associated with the metallization transition. If so, a structural change (B1→B2 or B1→B8) or spin‐pairing transition may not need to be invoked to explain the high pressure phase transition in FeO. Below the Neel temperature of FeO, antiferromagnetic ordering of Fe spins forces the Fe (t 2g ) electrons to be localized. Since the Neel temperature increases with pressure, no metallization transition of FeO was observed by Yagi et al. [1985] in their high‐pressure measurements at 300K. Neither (Mg, Fe)O and (Mg,Fe)SiO 3 can undergo a Mott transition at high pressure and temperature. Consequently, it is here argued that a lower mantle containing only these phases should be electrically insulating. Finally, the formation of itinerant d‐electrons in FeO may be a necessary, if not sufficient, condition for the apparent alloying of FeO with Fe. Such alloying may allow oxygen to be incorporated into the outer core.