scholarly journals Phase Relations of Earth’s Core-Forming Materials

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 581
Author(s):  
Tetsuya Komabayashi
Keyword(s):  
Binary Systems ◽  
Outer Core ◽  
Phase Relations ◽  
Future Research ◽  
Liquid Alloys ◽  
Longitudinal Wave Velocity ◽  
Earth’S Core ◽  
Earth's Core ◽  
Planetary Cores ◽  
Fe Alloys

Recent updates on phase relations of Earth’s core-forming materials, Fe alloys, as a function of pressure (P), temperature (T), and composition (X) are reviewed for the Fe, Fe-Ni, Fe-O, Fe-Si, Fe-S, Fe-C, Fe-H, Fe-Ni-Si, and Fe-Si-O systems. Thermodynamic models for these systems are highlighted where available, starting with 1 bar to high-P-T conditions. For the Fe and binary systems, the longitudinal wave velocity and density of liquid alloys are discussed and compared with the seismological observations on Earth’s outer core. This review may serve as a guide for future research on the planetary cores.

scholarly journals Fe5S2 identified as a host for sulfur in Earth’s core

2021 ◽  
Author(s):  
Claire Zurkowski ◽  
Barbara Lavina ◽  
Abigail Case ◽  
Kellie Swadba ◽  
Stella Chariton ◽  
...  
Keyword(s):  
Iron Sulfide ◽  
Inner Core ◽  
Outer Core ◽  
Iron Sulfides ◽  
Earth’S Core ◽  
Earth's Core ◽  
Planetary Cores ◽  
Wide Range ◽  
Metal Metal ◽  
The Stability

Planetary habitability, as we experience on Earth, is linked to a functioning geodynamo which is in part driven by the crystallization of the liquid iron-nickel-alloy core as a planet cools over time. Cosmochemical considerations suggest that sulfur is a candidate light alloying element in rocky planetary cores of varying sizes and oxidation states; such that, iron sulfide phase relations at extreme conditions contribute to outer core thermochemical convection and inner core crystallization in a wide range of planetary bodies. Here we experimentally investigate the structural properties of the Fe-S system and report the discovery of the sulfide, Fe5S2, crystallizing in equilibrium with iron at Earth’s outer core pressures and high temperatures. Using single-crystal X-ray diffraction techniques, Fe5S2 was determined to adopt the complex Ni5As2-type structure (P63cm, Z = 6). These results conclude that Fe5S2 is likely to crystallize at the interface of Earth’s core and mantle and will begin to crystallize during the freezing out of Earth and Venus’ core overtime. The increased metal-metal bonding measured in Fe5S2 compared to the other high P-T iron sulfides may contribute to signatures of higher conductivity from regions of Fe5S2 is crystallization. Fe5S2 could serve as a host for Ni and Si as has been observed in the related meteoritic phase, perryite, (Fe, Ni)8(P, Si)3, adding intricacies to elemental partitioning during inner core crystallization. The stability of Fe5S2 presented here is key to understanding the role of sulfur in the multicomponent crystallization sequences that drive the geodynamics and dictate the structures of Earth and rocky planetary cores.

Fast (non-)diffusive Quasi-Geostrophic Magneto-Coriolis Modes in the Earth's core

2021 ◽  
Author(s):  
Felix Gerick ◽  
Dominique Jault ◽  
Jerome Noir
Keyword(s):  
Magnetic Field ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
Outer Core ◽  
Equatorial Region ◽  
Earth’S Core ◽  
Earth's Core ◽  
Strong Focusing ◽  
Geomagnetic Observations ◽  
And Diffusion

<p> Fast changes of Earth's magnetic field could be explained by inviscid and diffusion-less quasi-geostrophic (QG) Magneto-Coriolis modes. We present a hybrid QG model with columnar flows and three-dimensional magnetic fields and find modes with periods of a few years at parameters relevant to Earth's core. These fast Magneto-Coriolis modes show strong focusing of their kinetic and magnetic energy in the equatorial region, while maintaining a relatively large spatial structure along the azimuthal direction. Their properties agree with some of the observations and inferred core flows. We find additionally, in contrast to what has been assumed previously, that these modes are not affected significantly by magnetic diffusion. The model opens a new way of inverting geomagnetic observations to the flow and magnetic field deep within the Earth's outer core.</p>

scholarly journals Phase relations of Fe-Si alloy in Earth's core

2009 ◽  
Vol 36 (6) ◽  
Author(s):  
Jung-Fu Lin ◽  
Henry P. Scott ◽  
Rebecca A. Fischer ◽  
Yun-Yuan Chang ◽  
Innokenty Kantor ◽  
...  
Keyword(s):  
Phase Relations ◽  
Earth’S Core ◽  
Earth's Core

scholarly journals Self-diffusion coefficient and sound velocity of Fe-Ni-O fluid: implications for the stratification of Earth’s outer core

2021 ◽  
Author(s):  
Wei-Jie Li ◽  
Zi Li ◽  
Chong-Jie Mo ◽  
Xian-Tu He ◽  
Cong Wang ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Sound Velocity ◽  
Outer Core ◽  
The Self ◽  
Ab Initio Molecular Dynamics ◽  
Earth Model ◽  
Earth’S Core ◽  
Earth's Core ◽  
Self Diffusion ◽  
Self Diffusion Coefficient

Abstract It is experimentally reported that the stratified layer atop Earth’s outer core is hundreds of kilometers thick with a maximum sound velocity reduction of 0.3% relative to the preliminary reference Earth model. However, why the sound velocity atop the outer core is reduced remains theoretically unclear. In this paper, the Ni and vital light O in the outer core were both considered to have implications for the stratification of Earth’s core, including the stratification thickness and the sound velocity profile. Ab initio molecular dynamics simulations were performed on the Fe-Ni-O fluid under the conditions of Earth’s outer core, and the self-diffusion coefficients and ion-ion dynamic structure factors were calculated. The self-diffusion coefficient of O is (19.56±0.83)×10-9 m2s-1 at the core-mantle boundary. Combining the diffusion equation with the time evolution of the O self-diffusion coefficient, the calculated stratification thickness at present is 194.7 km. The calculated ion-ion dynamic structural factors indicate that the sound velocity in the outmost outer core near the stratified layer is 7.86 km/s. These results show that Fe-Ni-O is a possible composition of the stratified layer atop the outer core featuring an appropriate thickness and a reduced sound velocity, thereby shedding light on the dynamic behavior of Earth’s core.

Can NASA’s Gravity Satellites Detect Motions in Earth’s Core?

Eos ◽  
2021 ◽  
Vol 102 ◽  
Author(s):  
Megan Kalomiris
Keyword(s):  
Gravitational Field ◽  
Outer Core ◽  
Earth’S Core ◽  
Earth's Core

Measurements of our planet’s gravitational field could expose processes in the fluid outer core—if scientists can decipher the signals.

scholarly journals Phase relations of Fe3 C and Fe7 C3 up to 185 GPa and 5200 K: Implication for the stability of iron carbide in the Earth's core

2016 ◽  
Vol 43 (24) ◽  
pp. 12,415-12,422 ◽  
Author(s):  
Jin Liu ◽  
Jung-Fu Lin ◽  
Vitali B. Prakapenka ◽  
Clemens Prescher ◽  
Takashi Yoshino
Keyword(s):  
Iron Carbide ◽  
Phase Relations ◽  
Earth’S Core ◽  
Earth's Core ◽  
The Stability

Phase relations in iron-rich systems and implications for the Earth's core

1989 ◽  
Vol 55 (3-4) ◽  
pp. 208-220 ◽  
Author(s):  
William W. Anderson ◽  
Bob Svendsen ◽  
Thomas J. Ahrens
Keyword(s):  
Phase Relations ◽  
Earth’S Core ◽  
Earth's Core

Thermodynamics from first principles: temperature and composition of the Earth’s core

2003 ◽  
Vol 67 (1) ◽  
pp. 113-123 ◽  
Author(s):  
D. Alfé ◽  
M. J. Gillan ◽  
G. D. Price
Keyword(s):  
Melting Temperature ◽  
First Principles ◽  
Inner Core ◽  
Melting Curve ◽  
Outer Core ◽  
Earth’S Core ◽  
Earth's Core ◽  
The Core ◽  
Core Conditions ◽  
Main Ideas

AbstractWe summarize the main ideas used to determine the thermodynamic properties of pure systems and binary alloys from first principles calculations. These are based on the ab initio calculations of free energies. As an application we present the study of iron and iron alloys under Earth,s core conditions. In particular, we report the whole melting curve of iron under these conditions, and we put constraints on the composition of the core. We found that iron melts at 6350士600 K at the pressure corresponding to the boundary between the solid inner core and the liquid outer core (ICB). We show that the core could not have been formed from a binary mixture of Fe with S, Si or O and we propose a ternary or quaternary mixture with 8—10% of S/Si in both liquid and solid and an additional ~8% of oxygen in the liquid. Based on this proposed composition we calculate the shift of melting temperature with respect to the melting temperature of pure Fe of ~—700 K, so that our best estimate for the temperature of the Earth's core at ICB is 5650±600 K.

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