High‐Pressure Phase Stability and Thermoelastic Properties of Iron Carbonitrides and Nitrogen in the Deep Earth

Huang, Shengxuan; Wu, Xiang; Zhu, Feng; Lai, Xiaojing; Li, Jie; Neill, Owen K.; Qin, Shan; Rapp, Robert P.; Zhang, Dongzhou; Dera, Przemysław; Chariton, Stella; Prakapenka, Vitali B.; Chen, Bin

doi:10.1029/2021jb021934

Cited by 3 publications

(5 citation statements)

References 71 publications

(170 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, neither the eutectic composition nor eutectic melting temperature under high pressures has been investigated yet. Considering the similarity in geochemical properties of carbon and nitrogen, it is beneficial to compare the high‐pressure melting behavior between the Fe–N and Fe–C systems (Huang et al., 2021; Sagatov et al., 2019). Although it remains controversial for the eutectic composition of 1.5 or 3.0 wt.% C in the Fe–C system, high P‐T experiments reached almost the same melting temperatures (Fei & Brosh, 2014; Liu, Li, et al., 2016; Lord et al., 2009; Morard et al., 2017).…”

Section: Resultsmentioning

confidence: 99%

“…Other iron nitrides like hcp ζ ‐Fe 2 N, nonstoichiometric ε ‐Fe 3 N x (0.75 < x < 1.5), and fcc γ ’‐Fe 4 N have also been experimentally confirmed to be stable up to 40–70 GPa at room temperature, but their thermal stability has not been well studied yet (Litasov et al., 2017). Additionally, the iron spin transition, equation of state, and electrical conductivity of these nitrides have recently been studied (Huang et al., 2021; Lv et al., 2020; Zhang & Yin, 2012; Zhuang et al., 2021).…”

Section: Introductionmentioning

confidence: 99%

“…Iron nitrides are likely the main nitrogen‐bearing species under reducing conditions in the deep Earth down to the core‐mantle boundary (CMB) while NH 3 and NH 4 + complexes are more abundant in shallow subduction zones (Huang et al., 2021; Speelmanns et al., 2018; Yoshioka et al., 2018). Naturally occurring iron nitrides have been frequently discovered, including orthorhombic Fe 2 N and trigonal Fe 3 N as inclusions in deep mantle diamonds from Rio Soriso, Brazil, and cubic Fe 4 N (roaldite) in iron meteorites (Kaminsky & Wirth, 2017; Niellsen & Burhwald, 1981).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Ultralow Melting of Iron Nitrides and the Fe–N–C System at High Pressure

Liu

2022

JGR Solid Earth

View full text Add to dashboard Cite

Nitrogen is not only crucial for organisms, but also an important tracer for the formation and evolution of terrestrial planets. CI chondrite meteorites were previously thought to represent the bulk composition of our planet; considerable amounts of nitrogen up to 5,000 ppm might have been stored on Earth (Adler & Williams, 2005;Sugiura, 1998). Recent studies suggest the bulk Earth accreted from 70% to 90% reduced enstatite chondrites followed by 10%-30% oxidized CI carbonaceous chondrites, and both chondrites could deliver excess nitrogen to the Earth (Dauphas, 2017;Grewal et al., 2019). However, the abundance of nitrogen in the bulk silicate Earth (BSE) is commonly assessed to be 0.84-33 ppm (

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Ultralow Melting of Iron Nitrides and the Fe–N–C System at High Pressure

Liu

2022

JGR Solid Earth

View full text Add to dashboard Cite

show abstract

“…Although Fe 7 N 3 -Pbca is thermodynamically unstable at inner core pressures, there is no imaginary mode in the phonon spectra (Figure S5), which means that it is dynamically stable. Recently, Huang et al 55 show the existence of the Fe 7 (N,C) 3 solid solution above 40 GPa. The stability of this solid solution was traced up to ∼60 GPa.…”

Section: ■ Computational Methodsmentioning

confidence: 99%

Fe–N System at High Pressures and Its Relevance to the Earth’s Core Composition

Sagatov

Sagatova

Gavryushkin

et al. 2021

Crystal Growth & Design

View full text Add to dashboard Cite

Based on ab initio calculations within the density functional theory and crystal structure prediction algorithms, the structure and stability of iron−nitrogen compounds in the pressure range of 100−400 GPa and temperatures up to 4000 K were determined. Three new iron nitrides Fe 4 N 3 -Imm2, Fe 2 N-Pnma, and Fe 3 N-C2/m were predicted. Fe 4 N 3 was shown to be stable at pressures up to 266 GPa and then decompose into Fe 2 N + 2FeN. Predicted Fe 2 N-Pnma becomes stable with respect to the decomposition reaction 9Fe 2 N = Fe 4 N 3 + 2Fe 7 N 3 at pressures above 221 GPa. Fe 3 N-C2/m stabilizes with respect to decomposition into 2Fe + Fe 7 N 3 at pressures above 265 GPa. Also, it was shown that β-Fe 7 N 3 synthesized in diamond anvil cell experiments has an orthorhombic Pbca structure, and at pressures above ∼320 GPa decomposes into 2Fe 2 N + Fe 3 N. All predicted Fe-rich iron nitrides, except Fe 4 N 3 -Imm2, have structural analogs among iron carbides. Considering the temperature effect, we observed that FeN-P2 1 3, Fe 2 N-Pnma, and Fe 3 N-C2/m can be stable at the Earth's inner core pressures and temperatures up to 4000 K, whereas Fe 4 N 3 -Imm2 and β-Fe 7 N 3 are thermodynamically unstable in the entire studied temperature range. Although Fe 7 N 3 -Pbca is thermodynamically unstable at inner core pressures, it shows the closest coincidence of the S-and P-wave velocities with seismic observations among the studied Fe-nitrides. Overall, Fe-nitrides cannot be the major compounds in the inner core of the Earth and can only substitute other elements such as carbon in Fe-carbides in minor amounts.

show abstract

“…These results indicate that in the Fe 0 ‐saturated mantle, N released from the slab preferentially partitions into the metallic Fe phase over the silicates. Despite the metallic Fe was proposed to be a potential host for subducted N in the deep mantle (Huang, Wu, et al., 2021; Lv & Liu, 2022), it remains unclear how N is transported from subducted slabs to the metallic Fe of the reduced mantle. It is also unknown whether the volatile‐rich metallic Fe is still capable of concentrating N from slabs.…”

Section: Introductionmentioning

confidence: 99%

Experimental Constraints on the Fate of Subducted Sedimentary Nitrogen in the Reduced Mantle

Huang

Chariton

et al. 2022

JGR Solid Earth

Self Cite

View full text Add to dashboard Cite

Nitrogen is considered to be transported from Earth′s surface to the top of the lower mantle through subduction. However, little is known on the transportation and fate of subducted nitrogen to the Earth′s interior during slab‐mantle interactions. In this study, the stability of subducted sedimentary nitrogen in the reduced mantle was investigated to 35 GPa and 1600 K by laser‐heated diamond anvil cell experiments and first‐principles calculations. Our results showed that subducted nitrogen‐bearing silicates and fluids could not coexist with the metallic iron or iron‐rich alloys, and reacted with them to form different products at high pressure‐temperature conditions. Combining our results with previous data, we re‐determined the relative stability of iron‐light element binary compounds to 35 GPa and 1600 K to be Fe‐O > Fe‐N > Fe‐S > Fe‐C. This stability sequence contributes to explaining the observation that iron nitrides are trapped as inclusions in sulfur‐depleted lower‐mantle diamonds and are absent in sulfur‐rich ones. The recycling efficiency of subducted sedimentary nitrogen is strongly related to the availability of the metallic iron of the reduced mantle. Hydration of the metallic iron limits the storage of nitrogen in it and contributes to recycling nitrogen to Earth′s surface. Therefore, unlike subducted continental sediments, subducted marine sediments are unlikely to transport a large amount of surficial nitrogen to the metallic iron of the reduced mantle in which nitrogen could reside over long geologic periods.

show abstract

High‐Pressure Phase Stability and Thermoelastic Properties of Iron Carbonitrides and Nitrogen in the Deep Earth

Cited by 3 publications

References 71 publications

Ultralow Melting of Iron Nitrides and the Fe–N–C System at High Pressure

Ultralow Melting of Iron Nitrides and the Fe–N–C System at High Pressure

Fe–N System at High Pressures and Its Relevance to the Earth’s Core Composition

Experimental Constraints on the Fate of Subducted Sedimentary Nitrogen in the Reduced Mantle

Contact Info

Product

Resources

About