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Structural Transitions in MgSiO 3 Glasses and Melts at the Core‐Mantle Boundary Observed via Inelastic X‐ray Scattering
Author(s) -
Kim YongHyun,
Yi Yoo Soo,
Kim HyoIm,
Chow Paul,
Xiao Yuming,
Shen Guoyin,
Lee Sung Keun
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl085889
Subject(s) - mantle (geology) , core–mantle boundary , materials science , scattering , buoyancy , outer core , molecular dynamics , spectral line , oxygen , inner core , geology , thermodynamics , physics , chemistry , optics , geophysics , computational chemistry , astronomy , composite material , quantum mechanics
The structural adaptation in MgSiO 3 melts under compression up to 130 GPa is the key to revealing the origins of the pronounced negative buoyancy of the melts at the core‐mantle boundary (CMB). A full understanding of the melt densification requires study of the pressure‐induced changes in the bonding configuration around oxygen at the CMB, which has proven to be difficult to measure. Here, the experimental breakthrough in O K ‐edge inelastic X‐ray scattering enables collection of the spectra of MgSiO 3 glasses up to ~130 GPa, along with ab initio molecular dynamics simulations, revealing the electronic bonding transitions around heavily compressed oxygen. The spectral results indicate the emergence of denser network structures around oxygen, stemming from contractions in the Mg‐O and O‐O distances associated with flexible topological and short‐range rearrangements around Si. The results unveil the electronic structure and thus the nature of densification in dense partial melts at the CMB.