title: Phase transition of FeO and stratification in Earth's outer core.
abstract: Light elements such as oxygen in Earth's core influence the physical properties of the iron alloys that exist in this region. Describing the high-pressure behavior of these materials at core conditions constrains models of core structure and dynamics. From x-ray diffraction measurements of iron monoxide (FeO) at high pressure and temperature, we show that sodium chloride (NaCl)-type (B1) FeO transforms to a cesium chloride (CsCl)-type (B2) phase above 240 gigapascals at 4000 kelvin with 2% density increase. The oxygen-bearing liquid in the middle of the outer core therefore has a modified Fe-O bonding environment that, according to our numerical simulations, suppresses convection. The phase-induced stratification is seismologically invisible but strongly affects the geodynamo.
authors.affiliation: Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa 237-0061, Japan. h-ozawa@jamstec.go.jp
authors.forename: Haruka
authors.initials: H
authors.lastname: Ozawa
authors.forename: Futoshi
authors.initials: F
authors.lastname: Takahashi
authors.forename: Kei
authors.initials: K
authors.lastname: Hirose
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ohishi
authors.forename: Naohisa
authors.initials: N
authors.lastname: Hirao