First-principles thermoelasticity and stability of pyrite-type FeO 2 under high pressure and temperature

Zhang, Xiu-Lu; Niu, Zhen-Wei; Tang, Mei; Zhao, Jianzhou; Cai, Ling-Cang

doi:10.1016/j.jallcom.2017.05.143

Cited by 10 publications

(16 citation statements)

References 23 publications

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“…The congruent melting temperatures of FeO 2 and FeO 2 H were calculated near CMB pressures as summarized in Figure . For FeO 2 , the melting temperature using GGA increases from 3,020 ± 30 K at 117 GPa to 3,415 ± 80 K at 156 GPa, in good agreement with the previous calculation (Zhang et al, ). For FeO 2 H, the melting temperature using GGA is in agreement with He et al () at 118 GPa but not at higher pressures.…”

Section: Resultssupporting

confidence: 90%

First‐Principles Study of FeO₂H_x Solid and Melt System at High Pressures: Implications for Ultralow‐Velocity Zones

et al. 2019

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Pyrite-type FeO 2 H x (P phase) has recently been suggested as a possible alternative to explain ultralow-velocity zones due to its low seismic velocity and high density. Here we report the results on the congruent melting temperature and melt properties of P phase at high pressures from first-principles molecular dynamics simulations. The results show that P phase would likely be melted near the core-mantle boundary. Liquid FeO 2 H x has smaller density and smaller bulk sound velocity compared to the isochemical P phase. As such, relatively small amounts of liquid FeO 2 H x could account for the observed seismic anomaly of ultralow-velocity zones. However, to maintain the liquid FeO 2 H x within the ultralow-velocity zones against compaction requires special physical conditions, such as relatively high viscosity of the solid matrix and/or vigorous convection of the overlying mantle.Plain Language Summary Ultralow-velocity zones (ULVZs) are 5-40-km-thick patches lying above Earth's core-mantle boundary. They are characterized with anomalously low seismic velocities compared with the ambient mantle and may contain important clues on the thermochemical evolution of the Earth. A recent experimental study argued that ULVZs may be caused by the accumulation of pyrite-type FeO 2 H x (P phase) at the bottom of the mantle. Here for the first time, we systematically study the thermoelastic properties of both FeO 2 H x solid and liquid phases. We find that P phase is likely melted near the core-mantle boundary and thus cannot be the source of ULVZs. Furthermore, in order for the molten product of P phase to cause ULVZs, the dense and nearly inviscid melts must be dynamically stable and confined within the ULVZs, which requires that the mantle is highly viscous and/or convects vigorously.

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Section: Resultssupporting

confidence: 90%

First‐Principles Study of FeO₂H_x Solid and Melt System at High Pressures: Implications for Ultralow‐Velocity Zones

et al. 2019

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“…The elastic constants of FeO 50 GPa, respectively, with C 44 value basically between 200 and 300 GPa. The effect of pressure on the elastic constants is consistent with previous results, 36,38 that with increasing temperature C 11 and C 12 reduce but there is no effect on C 44 . 38 Doped helium increases C 11 and C 44 , but has little effect on C 12 .…”

Section: Elastic Propertiessupporting

confidence: 91%

“…The variation of FeO 2 remains the same as in the previous results. 36,38 FeO 2 and FeO 2 He belong to the cubic crystal system with space groups Pa% 3 and Fm% 3m, respectively. The doped helium atom occupies the 4a position (0, 0, 0) of the iron atom in FeO 2 , and the iron atom occupies the 4b position (0, 0.5, 0), resulting in a 5.80-6.98% larger volume and a 1.15-2.27% lower density at 0-150 GPa in FeO 2 He compared to FeO 2 .…”

Section: Structural Propertiesmentioning

confidence: 99%

“…Based on the recent theoretical analysis 33 and the synthesis and characterization of FeO 2 , 27,28 the only viable solid heliumbearing compounds FeO 2 He and superionic FeO 2 H 2 He were discovered for the first time under the pressure-temperature conditions relevant to the core-mantle boundary. 34,35 Numerous studies suggest that FeO 2 is a feasible material composition for ULVZs, 28,36 and extensive research has been carried out on its crystal structure, 27,[37][38][39][40] atomic valence, 27,37,[41][42][43][44] conductivity, 36,37,45 magnetism, 44,46 and elasticity, 28,36,38 even though different results are difficult to coordinate. However, little is known about FeO 2 He compared to FeO 2 .…”

Section: Introductionmentioning

confidence: 99%

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

Liu

Xin

et al. 2023

Phys. Chem. Chem. Phys.

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“…It was commonly thought that all of the simplest iron oxides fall within three basic stoichiometries, such as FeO, Fe 3 O 4 , and Fe 2 O 3 . A recent series of high-pressure high-temperature (HP-HT) studies using single crystal X-ray diffraction methods discovered and identified a number of novel iron oxides, e.g., Fe 4 O 5 12 , 13 , Fe 5 O 6 14 , 15 , Fe 13 O 19 16 , Fe 5 O 7 17 , Fe 25 O 32 17 , FeO 2 18 – 21 , Fe 7 O 9 22 , and a new monoclinic polymorph of Fe 2 O 3 which can be stable at ambient conditions 23 . Some of the novel oxides, like Fe 4 O 5 , Fe 5 O 6 , and Fe 7 O 9 , were also found to be readily recoverable at ambient conditions.…”

Section: Introductionmentioning

confidence: 99%

Pressure tuning of charge ordering in iron oxide

et al. 2018

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A Verwey-type charge-ordering transition in magnetite at 120 K leads to the formation of linear units of three iron ions with one shared electron, called trimerons. The recently-discovered iron pentoxide (Fe4O5) comprising mixed-valent iron cations at octahedral chains, demonstrates another unusual charge-ordering transition at 150 K involving competing formation of iron trimerons and dimerons. Here, we experimentally show that applied pressure can tune the charge-ordering pattern in Fe4O5 and strongly affect the ordering temperature. We report two charge-ordered phases, the first of which may comprise both dimeron and trimeron units, whereas, the second exhibits an overall dimerization involving both the octahedral and trigonal-prismatic chains of iron in the crystal structure. We link the dramatic change in the charge-ordering pattern in the second phase to redistribution of electrons between the octahedral and prismatic iron chains, and propose that the average oxidation state of the iron cations can pre-determine a charge-ordering pattern.

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First-principles thermoelasticity and stability of pyrite-type FeO 2 under high pressure and temperature

Cited by 10 publications

References 23 publications

First‐Principles Study of FeO₂H_x Solid and Melt System at High Pressures: Implications for Ultralow‐Velocity Zones

First‐Principles Study of FeO₂H_x Solid and Melt System at High Pressures: Implications for Ultralow‐Velocity Zones

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

Pressure tuning of charge ordering in iron oxide

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First-principles thermoelasticity and stability of pyrite-type FeO 2 under high pressure and temperature

Cited by 10 publications

References 23 publications

First‐Principles Study of FeO2Hx Solid and Melt System at High Pressures: Implications for Ultralow‐Velocity Zones

First‐Principles Study of FeO2Hx Solid and Melt System at High Pressures: Implications for Ultralow‐Velocity Zones

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

Pressure tuning of charge ordering in iron oxide

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First‐Principles Study of FeO₂H_x Solid and Melt System at High Pressures: Implications for Ultralow‐Velocity Zones

First‐Principles Study of FeO₂H_x Solid and Melt System at High Pressures: Implications for Ultralow‐Velocity Zones

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