Stable magnesium peroxide at high pressure.
Rocky planets are thought to comprise compounds of Mg and O as these are among the most abundant elements, but knowledge of their stable phases may be incomplete. MgO is known to be remarkably stable to very high pressure and chemically inert under reduced condition of the Earth's lower mantle. However, in exoplanets oxygen may be a more abundant constituent. Here, using synchrotron x-ray diffraction in laser-heated diamond anvil cells, we show that MgO and oxygen react at pressures above 96 GPa and T = 2150 K with the formation of I4/mcm MgO2. Raman spectroscopy detects the presence of a peroxide ion (O2(2-)) in the synthesized material as well as in the recovered specimen. Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO. Our finding suggests that MgO2 may be present together or instead of MgO in rocky mantles and rocky planetary cores under highly oxidized conditions.
Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA.|V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk 630090, Russia.
Sergey S
SS
Lobanov
Department of Geosciences, Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794, USA.
Qiang
Q
Zhu
Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA.|Howard University, 2400 Sixth Street NW, Washington, DC 20059, USA.
Nicholas
N
Holtgrewe
Center for Advanced Radiation Sources, University of Chicago, Chicago, IL 60632, USA.
Clemens
C
Prescher
Center for Advanced Radiation Sources, University of Chicago, Chicago, IL 60632, USA.
Vitali B
VB
Prakapenka
Department of Geosciences, Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794, USA.|Moscow Institute of Physics and Technology, 9 Institutskiy lane, Dolgoprudny city, Moscow Region, 141700, Russian Federation.|School of Materials Science, Northwestern Polytechnical University, Xi'an, 710072, China.|Skolkovo Institute of Science and Technology, Skolkovo Innovation Center, 5 Nobel St., Moscow 143026, Russia.
Artem R
AR
Oganov
Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA.|Key Laboratory of Materials Physics, Institute of Solid State Physics, CAS, Hefei, 230031, China.|University of Science and Technology of China, Hefei, 230026, China.
Alexander F
AF
Goncharov