| Инд. авторы: | Litasov K.D., Shatskiy A., Ponomarev D.S, Gavryushkin P.N. |
| Заглавие: | Equations of state of iron nitrides ε-Fe3Nx and γ-Fe4Ny to 30 GPa and 1200 K and implication for nitrogen in the Earth's core |
| Библ. ссылка: | Litasov K.D., Shatskiy A., Ponomarev D.S, Gavryushkin P.N. Equations of state of iron nitrides ε-Fe3Nx and γ-Fe4Ny to 30 GPa and 1200 K and implication for nitrogen in the Earth's core // Journal of Geophysical Research: Solid Earth. - 2017. - Vol.122. - Iss. 5. - P.3574-3584. - ISSN 2169-9313. - EISSN 2169-9356. |
| Внешние системы: | DOI: 10.1002/2017JB014059; РИНЦ: 31034170; SCOPUS: 2-s2.0-85019921988; WoS: 000403465600018; |
| Реферат: | eng: Nitrogen abundance is one of the most uncertain among all elements in the Earth's interior. Recent data indicate an affinity between Fe-nitrides and Fe-carbides in the Earth's mantle and inner core. In this work P-V-T equations of state of ε-Fe3N0.8 and ε-Fe3N1.26 (which is close to Fe7N3) have been determined using a combination of multianvil and synchrotron radiation techniques at pressures up to 30 GPa and temperatures up to 1473 K. A fit of the P-V-T data to the Vinet-Rydberg and Mie-Grüneisen-Debye equations of state yields the following thermoelastic parameters for the ε-Fe3N0.8: V0 = 81.44(2) Å3, KT0 = 157(3) GPa, KT′ = 5.3 (fixed), θ0 = 555 K (fixed), γ0 = 1.83(1), and q = 1.34(18). For ε-Fe3N1.26 we obtained V0 = 86.18(2) Å3, KT0 = 163(2) GPa, KT′ = 5.3(2), θ0 = 562(90) K, γ0 = 1.85(2), and q = 0.55(24). It is likely that all presumably paramagnetic ε-Fe3Nx with x = 0.75–1.5 have similar thermoelastic properties with a minor increase of the bulk modulus with increasing N content. The melting temperature of ε-Fe3Nx increases from approximately 1473 to 1573 K in the pressure range from 5 to 30 GPa. We also determined a preliminary equation of state for γ-Fe4Ny and calculated y = 0.35(2) from the data at 20–30 GPa. Combining the results with a recent experimental study on the stability of β-Fe7N3, isostructural with Fe7C3, and a theoretical study of the magnetic transitions in ε-Fe3Nx, we estimate the density of Fe-nitrides at the Earth's inner core conditions. Our results indicate that at 5000–6000 K, 2.0–3.2 wt % N can explain the density deficit in Earth's inner core. ©2017. American Geophysical Union. All Rights Reserved.
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| Ключевые слова: | nitrogen; iron; equation of state; core (planetary); bulk modulus; nitrogen; nitride; iron; equation of state; Earth's core; thermoelasticity; |
| Издано: | 2017 |
| Физ. характеристика: | с.3574-3584 |