High-pressure experimental and computational XANES studies of(Mg,Fe)(Si,Al)O3perovskite and (Mg,Fe)O ferropericlase as in the Earth’s lower mantle

2009 ◽  
Vol 79 (17) ◽  
Author(s):  
O. Narygina ◽  
M. Mattesini ◽  
I. Kantor ◽  
S. Pascarelli ◽  
X. Wu ◽  
...  
Keyword(s):  
High Pressure ◽  
Lower Mantle

scholarly journals From Slater to Mott physics by epitaxially engineering electronic correlations in oxide interfaces

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Carla Lupo ◽  
Evan Sheridan ◽  
Edoardo Fertitta ◽  
David Dubbink ◽  
Chris J. Pickard ◽  
...  
Keyword(s):  
Phase Diagram ◽  
High Pressure ◽  
Charge Transfer ◽  
Lower Mantle ◽  
Random Structure ◽  
Titanium Oxides ◽  
Oxide Interfaces ◽  
Electronic Correlations ◽  
Epitaxial Strain ◽  
Magnetic Switching

AbstractUsing spin-assisted ab initio random structure searches, we explore an exhaustive quantum phase diagram of archetypal interfaced Mott insulators, i.e. lanthanum-iron and lanthanum-titanium oxides. In particular, we report that the charge transfer induced by the interfacial electronic reconstruction stabilises a high-spin ferrous Fe2+ state. We provide a pathway to control the strength of correlation in this electronic state by tuning the epitaxial strain, yielding a manifold of quantum electronic phases, i.e. Mott-Hubbard, charge transfer and Slater insulating states. Furthermore, we report that the electronic correlations are closely related to the structural oxygen octahedral rotations, whose control is able to stabilise the low-spin state of Fe2+ at low pressure previously observed only under the extreme high pressure conditions in the Earth’s lower mantle. Thus, we provide avenues for magnetic switching via THz radiations which have crucial implications for next generation of spintronics technologies.

Partitioning of Fe within high-pressure silicate perovskite: Evidence for unusual geochemistry in the lower mantle

1987 ◽  
Vol 14 (3) ◽  
pp. 224-226 ◽  
Author(s):  
W. E. Jackson ◽  
E. Knittle ◽  
G. E. Brown ◽  
R. Jeanloz
Keyword(s):  
High Pressure ◽  
Lower Mantle

scholarly journals Mineralogy of the deep lower mantle in the presence of H2O

2020 ◽  
Author(s):  
Qingyang Hu ◽  
Jin Liu ◽  
Jiuhua Chen ◽  
Bingmin Yan ◽  
Yue Meng ◽  
...  
Keyword(s):  
High Pressure ◽  
Lower Mantle ◽  
Excessive Amount ◽  
Internal Source ◽  
Charge Balance ◽  
Oxide Mineral ◽  
Oxygen Excess ◽  
Excess Phase ◽  
Earth’S Interior ◽  
Mg Content

Abstract Understanding the mineralogy of the Earth's interior is a prerequisite for unravelling the evolution and dynamics of our planet. Here, we conducted high pressure-temperature experiments mimicking the conditions of the deep lower mantle (DLM, 1800–2890 km in depth) and observed surprising mineralogical transformations in the presence of water. Ferropericlase, (Mg, Fe)O, which is the most abundant oxide mineral in Earth, reacts with H2O to form a previously unknown (Mg, Fe)O2Hx (x ≤ 1) phase. The (Mg, Fe)O2Hx has a pyrite structure and it coexists with the dominant silicate phases, bridgmanite and post-perovskite. Depending on Mg content and geotherm temperatures, the transformation may occur at 1800 km for (Mg0.6Fe0.4)O or beyond 2300 km for (Mg0.7Fe0.3)O. The (Mg, Fe)O2Hx is an oxygen excess phase that stores an excessive amount of oxygen beyond the charge balance of maximum cation valences (Mg2+, Fe3+ and H+). This important phase has a number of far-reaching implications including extreme redox inhomogeneity, deep-oxygen reservoirs in the DLM and an internal source for modulating oxygen in the atmosphere.

scholarly journals Evidence for the charge disproportionation of iron in extraterrestrial bridgmanite

2020 ◽  
Vol 6 (2) ◽  
pp. eaay7893 ◽  
Author(s):  
Luca Bindi ◽  
Sang-Heon Shim ◽  
Thomas G. Sharp ◽  
Xiande Xie
Keyword(s):  
High Pressure ◽  
Metallic Iron ◽  
Valence State ◽  
Lower Mantle ◽  
Direct Evidence ◽  
Mixed Valence ◽  
Disproportionation Reaction ◽  
Redox Processes ◽  
Charge Disproportionation ◽  
Suizhou Meteorite

Bridgmanite, MgSiO3 with perovskite structure, is considered the most abundant mineral on Earth. On the lower mantle, it contains Fe and Al that strongly influence its behavior. Experimentalists have debated whether iron may exist in a mixed valence state, coexistence of Fe2+ and Fe3+ in bridgmanite, through charge disproportionation. Here, we report the discovery of Fe-rich aluminous bridgmanite coexisting with metallic iron in a shock vein of the Suizhou meteorite. This is the first direct evidence in nature of the Fe disproportionation reaction, which so far has only been observed in some high-pressure experiments. Furthermore, our discovery supports the idea that the disproportionation reaction would have played a key role in redox processes and the evolution of Earth.

Density and composition of the lower mantle

1989 ◽  
Vol 328 (1599) ◽  
pp. 377-389 ◽  
Keyword(s):  
High Pressure ◽  
Density Distribution ◽  
Upper Mantle ◽  
Lower Mantle ◽  
Mineral Assemblage ◽  
Geophysical Data ◽  
Density Difference ◽  
Depth Range ◽  
Density Measurements ◽  
Mantle Composition

The observed density distribution of the lower mantle is compared with density measurements of the (M g,Fe)SiO 3 perovskite and (Mg,Fe)O magnesiowtistite highpressure phases as functions of pressure, tem perature and composition. We find that for plausible bounds on the composition of the upper mantle (ratio of magnesium to iron + magnesium components x M g ^ 0.88) and the temperature in the lower mantle ( T ^ 2000 K), the high-pressure mineral assemblage of upper-mantle composition is at least 2 .6 ( ± 1 ) % less dense than the lower m antle over the depth range 1000-2000 km. Thus, we find that a model of uniform m antle composition is incompatible with the existing mineralogical and geophysical data. Instead, we expect that the mantle is stratified, with the upper and lower m antle convecting separately, and we estimate that the compositional density difference between these regions is about 5 ( + 2) %. The stratification may not be perfect (‘leaky layering’), but significant intermixing and homogenization of the upper and lower m antle over geological timescales are precluded.

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