Journal Article

PUBDB-2026-01064

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Sulfur‐Bearing hcp Iron for Earth's Inner Core

Sugimura-Komabayashi, E. (Corresponding author) ; Thompson, S.Extern* ; Komabayashi, T. (Corresponding author)Extern* ; Freitas, D.Extern* ; Robertson, M. ; Giordano, N.DESY* ; Pakhomova, A.Extern* ; Liermann, H.-P.XFEL.EU*DESY*

2026
Wiley Hoboken, NJ

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Please use a persistent id in citations: doi:10.1029/2025GL121618  doi:10.3204/PUBDB-2026-01064

Abstract: Earth's iron core is believed to contain light impurities which should have been included during core formation. In order to place constraints on core composition, here we report the effect of sulfur on density of hexagonal close-packed (hcp) iron which was not previously examined, using laser-heated diamond anvil cells with in situ synchrotron X-ray diffraction. Results show that the unit-cell volume for 2 wt% sulfur-bearing hcp iron is indistinguishable from that for pure iron at 300 K and smaller at high temperatures under core pressures. This gives rise to a moderately dense hcp phase which can explain the observed large density jump across the inner core-outer core boundary (ICB). A self-consistent core model was established with Fe-5.1 ± 0.6wt%Si-2.0 ± 0.6wt%S-0.7 ± 0.6wt%O for the outer core and Fe-5.1 ± 0.2wt%Si-2.0 ± 0.6wt%S for the inner core with an ICB temperature of 5,730 K, which is geochemically defensible and supports the equilibrium core formation scenario.

Note: This paper was also funded by the following two grants in the UK. (i)The crystallisation sequence of Earth's core, NE/W005832/1, Natural Environment Research Council (NERC); (ii)Cryo-FIB-SEM-CT: a 'three-in-one' imaging facility for opaque soft matter, EP/P030564/1, Engineering and Physical Sciences Research Council (EPSRC)

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Contributing Institute(s):

1. DOOR-User (DOOR ; HAS-User)
2. PETRA-D (FS-PETRA-D)

Research Program(s):

1. 631 - Matter – Dynamics, Mechanisms and Control (POF4-631) (POF4-631)
2. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)
3. FS-Proposal: I-20190593 EC (I-20190593-EC) (I-20190593-EC)
4. FS-Proposal: I-20220483 (I-20220483) (I-20220483)
5. Earth core - Exploring Thermodynamic Properties of Earth’s Core-Forming Materials (647723) (647723)

Experiment(s):

1. PETRA Beamline P02.2 (PETRA III)

Appears in the scientific report 2026

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