Skip to content
Licensed Unlicensed Requires Authentication Published by De Gruyter November 29, 2019

Static compression of Fe4N to 77 GPa and its implications for nitrogen storage in the deep Earth

Helene Breton , Tetsuya Komabayashi EMAIL logo , Samuel Thompson , Nicola Potts , Christopher McGuire , Sho Suehiro , Simone Anzellini and Yasuo Ohishi
From the journal American Mineralogist


Compression and decompression experiments on face-centered cubic (fcc) γʹ-Fe4N to 77 GPa at room temperature were conducted in a diamond-anvil cell with in situ X‑ray diffraction (XRD) to examine its stability under high pressure. In the investigated pressure range, γʹ-Fe4N did not show any structural transitions. However, a peak broadening was observed in the XRD patterns above 60 GPa. The obtained pressure-volume data to 60 GPa were fitted to the third-order Birch-Murnaghan equation of state (EoS), which yielded the following elastic parameters: K0 = 169 (6) GPa, K′ = 4.1 (4), with a fixed V0 = 54.95 Å at 1 bar. A quantitative Schreinemakers’ web was obtained at 15–60 GPa and 300–1600 K by combining the EoS for γʹ-Fe4N with reported phase stability data at low pressures. The web indicates the existence of an invariant point at 41 GPa and 1000 K where γʹ-Fe4N, hexagonal closed-packed (hcp) ε-Fe7N3, double hexagonal closed-packed β-Fe7N3, and hcp Fe phases are stable. From the invariant point, a reaction γʹ-Fe4N = β-Fe7N3 + hcp Fe originates toward the high-pressure side, which determines the high-pressure stability of γʹ-Fe4N at 56 GPa and 300 K. Therefore, the γʹ-Fe4N phase observed in the experiments beyond this pressure must be metastable. The obtained results support the existing idea that β-Fe7N3 would be the most nitrogen-rich iron compound under core conditions. An iron carbonitride Fe7(C,N)3 found as a mantle-derived diamond inclusion implies that β-Fe7N3 and Fe7C3 may form a continuous solid solution in the mantle deeper than 1000 km depth. Diamond formation may be related to the presence of fluids in the mantle, and dehydration reactions of high-pressure hydrous phase D might have supplied free fluids in the mantle at depths greater than 1000 km. As such, the existence of Fe7(C,N)3 in diamond can be an indicator of water transportation to the deep mantle.

Orcid 0000-0002-1106-1592

† Special collection papers can be found online at

Acknowledgments and Funding

We thank K. Litasov and an anonymous reviewer for their helpful comments on the manuscript. Synchrotron XRD measurements were carried out at beamlines BLI15 at the Diamond Light Source (ref number: ee17683-1) and BL10XU at the SPring-8 (ref number: 2018B1464). This work is supported by the Natural Environment Research Council (NERC) (No. NE/M000346/1) and by the European Research Council (ERC) Consolidator Grant to T.K. (No. 647723).

References cited

Adler, J.F., and Williams, Q. (2005) A high-pressure X‑ray diffraction study of iron nitrides: Implications for Earth’s core. Journal of Geophysical Research, 110, 1–11.10.1029/2004JB003103Search in Google Scholar

Anzellini, S., Kleppe, A.K., Daisenberger, D., Wharmby, M.T., Giampaoli, R., Broccato, S., Baron, M.A., Miozzi, F., Keeble, D.S., Ross, A., and others. (2018) Laser-heating system for high-pressure X‑ray diffraction at the extreme conditions beamline I15 at Diamond Light Source. Journal of Synchrotron Radiation, 25, 1860–1868.10.1107/S1600577518013383Search in Google Scholar

Bajgain, S., Mookherjee, M., Dasgupta, R., Gosh, D.B., and Karki, B.B. (2018) Nitrogen content in the Earth’s outer. Geophysical Research Letter, 46, 89–98.10.1029/2018GL080555Search in Google Scholar

Birch, F. (1952) Elasticity and constitution of the Earth’s interior. Journal of Geophysical Research, 57, 227–286.10.1029/SP026p0031Search in Google Scholar

Cartigny, P. (2005) Stable isotopes and the origin of diamond. Elements, 1(2), 79–84.10.2113/gselements.1.2.79Search in Google Scholar

Dewaele, A., Loubeyre, P., Occelli, F., Mezouar, M., Dorogokupets, P.I., and Torrent, M. (2006) Quasihydrostatic equation of state of iron above 2Mbar. Physical Review Letters, 97, 215504.10.1103/PhysRevLett.97.215504Search in Google Scholar

Dewaele, A., Belonoshko, A.B., Garbarino, G., Occelli, F., Bouvier, P., Hanfland, M., and Mezouar, M. (2012) High-pressure–high-temperature equation of state of KCl and KBr . Physical Review B, 85, 214105.10.1103/PhysRevB.85.214105Search in Google Scholar

Fei, Y., Murphy, C., Shibazaki, Y., Shahar, A., and Huang, H. (2016) Thermal equation of state of hcp-iron: Constraint on the density deficit of Earth’s solid inner core. Geophysical Research Letters, 43, 6837–6843.10.1002/2016GL069456Search in Google Scholar

Gavryushkin, P.N., Sagatov, N.E., Popov, Z.I., Bekhtenova, A.E., Inerbaev, T.M., and Litasov, K.D. (2018) Structure and properties of new high-pressure phase of Fe7N3 JETP Letters, 107(6), 379–383.10.1134/S0021364018060061Search in Google Scholar

Göhring, H., Fabrichnaya, O., Leineweber, A., and Mittemeijer, E.J. (2016) Thermodynamics of the Fe-N and Fe-N-C systems: the Fe-N and Fe-N-C phase diagrams revisited. Metallurgical and Materials Transactions A, 47 A, 6173–6186.10.1007/s11661-016-3731-0Search in Google Scholar

Guo, K., Rau, D., Von Appen, J., Prots, Y., Schnelle, W., Dronkowski, R., Niewa, R., and Schwarz, U. (2013) High pressure high-temperature behavior and magnetic properties of Fe4N: experiment and theory. High Pressure Research, 33, 684–696.10.1080/08957959.2013.809715Search in Google Scholar

Hammersley, A.P. (1996) FIT2D: a multi-purpose data reduction, analysis and visualization program. Journal of Applied Crystallography, 49, 646–652.10.1107/S1600576716000455Search in Google Scholar

Harte, B. (2010) Diamond formation in the deep mantle: the record of mineral inclusions and their distribution in relation to mantle dehydration zones. Mineralogical Magazine, 74, 189–215.10.1180/minmag.2010.074.2.189Search in Google Scholar

Jacobs, H., Rechenbach, D., and Zachwieja, U. (1995) Structure determination of γʹ-Fe4N and ε-Fe3N. Journal of Alloys and Compounds, 227, 10–17.10.1016/0925-8388(95)01610-4Search in Google Scholar

Kaminsky, F., and Wirth, R. (2011) Iron carbide inclusions in lower-mantle diamond from Juina, Brazil. Canadian Mineralogist, 49, 555–572.10.3749/canmin.49.2.555Search in Google Scholar

Komabayashi, T. (2006) Phase relations of hydrous peridotite: implications for water circulation in the Earth’s mantle. In S. Jacobsen and S. van der Lee, Eds., Earth’s Deep Water Cycle, p. 29–43. AGU.10.1029/168GM04Search in Google Scholar

Komabayashi, T. (2014) Thermodynamics of melting relations in the system Fe-FeO at high pressure: Implication for oxygen in the Earth’s core. Journal of Geophysical Research, 119, 4164–4177.10.1002/2014JB010980Search in Google Scholar

Komabayashi, T., Hirose, K., Sata, N., Ohishi, Y., and Dubronsky, L.S. (2007) Phase transition in CaSiO3 perovskite. Earth and Planetary Science Letters, 260, 564–569.10.1016/j.epsl.2007.06.015Search in Google Scholar

Komabayashi, T., Fei, Y., Meng, Y., and Prakapenka, V. (2009) In-situ X‑ray diffraction measurements of the γ-ε transition boundary of iron in an internally-heated diamond anvil cell. Earth and Planetary Science Letters, 282, 252–257.10.1016/j.epsl.2009.03.025Search in Google Scholar

Leineweber, A., Jacobs, H., Hüning, F., Lueken, H., Schilder, H., and Kockelmann, W. (1999) ε-Fe3N: magnetic structure, magnetization and temperature dependent disorder of nitrogen. Journal of Alloys and Compounds, 288, 79–87.10.1016/S0925-8388(99)00150-4Search in Google Scholar

Litasov, K.D., Shatskiy, A.F., Ovchinnikov, S.G., Popov, Z.I., Ponomarev, D.S., and Ohtani, E. (2013) Phase transformations of Fe3N–Fe4N iron nitrides at pressures up to 30 GPa studied by in situ X‑ray diffractometry. JETP Letters, 98, 805–808.10.1134/S0021364013250140Search in Google Scholar

Litasov, K.D., Shatskiy, A.F., Ponomarev, D.S., and Gavryushkin, P.N. (2017) 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, 122, 3574–3584.10.1002/2017JB014059Search in Google Scholar

Mikhail, S., Barry, P.H., and Sverjensky, D.A. (2017) The relationship between mantle pH and the deep nitrogen cycle. Geochimica et Cosmochimica Acta, 209, 149–160.10.1016/j.gca.2017.04.007Search in Google Scholar

Minobe, S., Nakajima, Y., Hirose, K., and Ohishi, Y. (2015) Stability and compressibility of a new iron-nitride β-Fe7N3 to core pressures. Geophysical Research Letters, 42, 5206–5211.10.1002/2015GL064496Search in Google Scholar

Nakajima, Y., Takahashi, E., Sata, N., Nishihara, Y., Hirose, K., Funakoshi, k.-I., and Ohishi, Y. (2011) Thermoelastic property and high-pressure stability of Fe7C3 Implication for iron-carbide in the Earth’s core. American Mineralogist, 96, 1158–1165.10.2138/am.2011.3703Search in Google Scholar

Narygina, O., Dubrovinsky, L.S., McCammon, C.A., Kurnosov, A., Kantor, I.Y., Prakapenka, V.B., and Dubrovinskaia, N.A. (2011) X-ray diffraction and Mössbauer spectroscopy study of fcc iron hydride FeH at high pressures and implications for the composition of the Earth’s core. Earth and Planetary Science Letters, 307, 409–414.10.1016/j.epsl.2011.05.015Search in Google Scholar

Niewa, R., Rau, D., Wosylus, A., Meier, K., Wessel, M., Hanfland, M., Dron-skowski, R., and Schwarz, U. (2009) High-pressure high-temperature phase transition of γʹ-Fe4N. Journal of Alloys and Compounds, 480, 76–80.10.1016/j.jallcom.2008.09.178Search in Google Scholar

Nishi, M., Irifune, T., Tsuchiya, J., Tange, Y., Nishihara, Y., Fujino, K., and Higo, Y. (2014) Stability of hydrous silicate at high pressures and water transport to the deep lower mantle. Nature Geoscience, doi:10.1038/NGEO2074.10.1038/NGEO2074Search in Google Scholar

Nomura, R., Hirose, K., Uesugi, K., Ohishi, Y., Tsuchiyama, A., Miyake, A., and Ueno, Y. (2014) Low core-mantle boundary temperature inferred from the solidus of pyrolite. Science, 343, 522–525.10.1126/science.1248186Search in Google Scholar

Ohishi, Y., Hirao, N., Sata, N., Hirose, K., and Takata, M. (2008) Highly intense monochromatic X‑ray diffraction facility for high-pressure research at SPring-8. High Pressure Research, 28, 163–173.10.1080/08957950802208910Search in Google Scholar

Okuchi, T. (1997) Hydrogen partitioning into molten iron at high pressure: Implications for Earth’s core. Science, 278, 1781–1784.10.1126/science.278.5344.1781Search in Google Scholar

Poirier, J.-P. (1994) Light elements in the Earth’s outer core: A critical review. Physics of the Earth and Planetary Interiors, 85, 319–337.10.1016/0031-9201(94)90120-1Search in Google Scholar

Sokolova, T.S, Dorogokupets, P.I., Dymshits, A.M., Danilov, B.S., and Litasov, K.D. (2016) Microsoft Excel spreadsheets for calculation of PVT relations and thermodynamic properties from equations of state of MgO, diamond and nine metals as pressure markers in high-pressure and high-temperature experiments. Computers and Geosciences, 94, 162–169.10.1016/j.cageo.2016.06.002Search in Google Scholar

Tateno, S., Kuwayama, Y., Hirose, K., and Ohishi, Y. (2015) The structure of Fe–Si alloy in Earth’s inner core. Earth and Planetary Science Letters, 418, 11–19.10.1016/j.epsl.2015.02.008Search in Google Scholar

Widenmeyer, M., Hansen, T.C., Meissner, E., and Niewa, R. (2014) Formation and decomposition of iron nitrides observed by in situ powder neutron diffraction and thermal analysis. Journal of Inorganic and General Chemistry, 640, 1265–1274.10.1002/zaac.201300676Search in Google Scholar

Received: 2019-03-26
Accepted: 2019-08-25
Published Online: 2019-11-29
Published in Print: 2019-12-18

© 2019 Walter de Gruyter GmbH, Berlin/Boston

Downloaded on 2.12.2022 from
Scroll Up Arrow