A first-principles study of the structural, electronic and elastic properties of the FeO2–FeO2He system under high pressure

Haibo Liu; Lei Liu; Cunlin Xin; Longxing Yang; Xiaoyu Gu

doi:10.1039/D3CP02315J

A first-principles study of the structural, electronic and elastic properties of the FeO₂–FeO₂He system under high pressure†

Haibo Liu,

*^a Lei Liu,*^b Cunlin Xin,^c Longxing Yang^d and Xiaoyu Gu^b

Author affiliations

* Corresponding authors

^a Key Laboratory of Geoscience Big Data and Deep Resource of Zhejiang Province, School of Earth Sciences, Zhejiang University, Hangzhou 310027, China
E-mail: haibo@zju.edu.cn

^b United Laboratory of High-Pressure Physics and Earthquake Science, Institute of Earthquake Forecasting, China Earthquake Administration, Beijing 100036, China
E-mail: liulei@ief.ac.cn

^c College of Geography and Environmental Science, Northwest Normal University, Lanzhou 730070, China

^d State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China

Abstract

The origin of the wave velocity anomalies at the core–mantle boundary (CMB) has been controversial. The primordial helium reservoir in the deep lower mantle remains elusive even with geochemical evidence for its existence. Here, we calculated the density and wave velocity of the FeO₂–FeO₂He system under the CMB conditions using first principles. The FeO₂ and FeO₂He of pyrite-type can exist stably under the CMB conditions without melting, and the incorporated helium increases the stability of the system. The electrical properties of FeO₂ and FeO₂He are not related to pressure. Doped helium reduces the density of the system but increases the elastic modulus. Our results suggest that FeO₂ can be used as a viable material composition of ultra-low velocity zones (ULVZs), and FeO₂He can explain the D′′ seismic discontinuity instead of ULVZs. The primordial helium reservoir possibly formed by the accumulation of FeO₂He, the only stable solid helium-bearing compound under the CMB conditions, may coincide with the location of the D′′ layer.

This article is part of the themed collection: 2023 PCCP HOT Articles

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Article information

DOI: https://doi.org/10.1039/D3CP02315J
Article type: Paper
Submitted: 22 May 2023
Accepted: 11 Jul 2023
First published: 11 Jul 2023

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Phys. Chem. Chem. Phys., 2023,25, 20225-20234

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A first-principles study of the structural, electronic and elastic properties of the FeO₂–FeO₂He system under high pressure

H. Liu, L. Liu, C. Xin, L. Yang and X. Gu, Phys. Chem. Chem. Phys., 2023, 25, 20225 DOI: 10.1039/D3CP02315J

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