Phase diagram of dense oxygen and nitrogen binary systems

Wan Xu; Veronika Afonina; Ross T. Howie; Eugene Gregoryanz

doi:10.1063/5.0317277

Volume 11 Issue 5

Sep. 2026

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Wan Xu, Veronika Afonina, Ross T. Howie, Eugene Gregoryanz. Phase diagram of dense oxygen and nitrogen binary systems[J]. Matter and Radiation at Extremes, 2026, 11(5): 057802. doi: 10.1063/5.0317277

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Wan Xu, Veronika Afonina, Ross T. Howie, Eugene Gregoryanz. Phase diagram of dense oxygen and nitrogen binary systems[J]. Matter and Radiation at Extremes, 2026, 11(5): 057802. doi: 10.1063/5.0317277

Wan Xu, Veronika Afonina, Ross T. Howie, Eugene Gregoryanz. Phase diagram of dense oxygen and nitrogen binary systems[J]. Matter and Radiation at Extremes, 2026, 11(5): 057802. doi: 10.1063/5.0317277

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Phase diagram of dense oxygen and nitrogen binary systems

doi: 10.1063/5.0317277

Wan Xu^1
,,
Veronika Afonina^2
,,
Ross T. Howie^{2, 3
,
,
,},
Eugene Gregoryanz^{1, 2, 3
,
,
,}

1.
Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
2.
Centre for Science at Extreme Conditions and School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
3.
Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China

More Information

Corresponding author: a)Authors to whom correspondence should be addressed: ross.howie@hpstar.ac.cn and e.gregoryanz@ed.ac.uk
Received Date: 2025-12-17
Accepted Date: 2026-05-25

Available Online: 2026-09-28

Publish Date: 2026-09-01

Abstract

Abstract

Through a series of high-pressure Raman scattering and X-ray diffraction experiments on N₂–O₂ binary mixtures with oxygen concentrations varying from 10% to 77%, we systematically explore the molecular interactions of the mixtures. Our study greatly extends the room-temperature phase diagram for the N₂–O₂ system from 12 to ∼60 GPa for all concentrations and up to ∼160 GPa for 28% of oxygen. A complex phase coexistence is observed below 17 GPa in O₂-rich mixtures, while in N₂-rich mixtures, the δ-to-ɛ transition of O₂ is shifted to higher pressures. Above 17 GPa, the mixture appears structurally as a composite of the ɛ–O₂ + ɛ–N₂ phase with the volume of oxygen being different from that of the pure element. Upon further compression, both elements broadly follow the phase transition sequence of the pure species, implying an absence of interactions and miscibility. Furthermore, oxygen metallization in the mixture occurs within a pressure range analogous to that of the pure sample, while above 130 GPa, amorphization and dissociation of nitrogen dominates, leading to the vibrational peaks of both O₂ and N₂ becoming weak.

Conflict of Interest
The authors have no conflicts to disclose.
Author Contributions
Wan Xu: Data curation (equal); Formal analysis (equal); Investigation (equal); Writing – original draft (equal); Writing – review & editing (equal). Veronika Afonina: Data curation (equal); Formal analysis (equal). Ross T. Howie: Data curation (equal); Formal analysis (equal). Eugene Gregoryanz: Formal analysis (equal); Supervision (equal); Writing – review & editing (equal).
The data that support the findings of this study are available within the article and its supplementary material and from the corresponding authors upon reasonable request.

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References(44)

References

[1]	D. K. Spaulding, G. Weck, P. Loubeyre, F. Datchi, P. Dumas et al., “Pressure-induced chemistry in a nitrogen–hydrogen host-guest structure,” Nat. Commun. 5, 5739 (2014).10.1038/ncomms6739
[2]	R. Turnbull, M.-E. Donnelly, M. Wang, M. Peña Alvarez, C. Ji et al., “Reactivity of hydrogen–helium and hydrogen–nitrogen mixtures at high pressures,” Phys. Rev. Lett. 121, 195702 (2018).10.1103/physrevlett.121.195702
[3]	M. S. Somayazulu, L. W. Finger, R. J. Hemley, and H. K. Mao, “High-pressure compounds in methane-hydrogen mixtures,” Science 271, 1400–1402 (1996).10.1126/science.271.5254.1400
[4]	U. Ranieri, L. J. Conway, M.-E. Donnelly, H. Hu, M. Wang et al., “Formation and stability of dense methane-hydrogen compounds,” Phys. Rev. Lett. 128, 215702 (2022).10.1103/physrevlett.128.215702
[5]	R. Bini, L. Ulivi, J. Kreutz, and H. J. Jodl, “High-pressure phases of solid nitrogen by Raman and infrared spectroscopy,” J. Chem. Phys. 112, 8522–8529 (2000).10.1063/1.481455
[6]	E. Gregoryanz, A. F. Goncharov, R. J. Hemley, H.-k. Mao, M. Somayazulu et al., “Raman, infrared, and x-ray evidence for new phases of nitrogen at high pressures and temperatures,” Phys. Rev. B 66, 224108 (2002).10.1103/physrevb.66.224108
[7]	E. Gregoryanz, A. F. Goncharov, C. Sanloup, M. Somayazulu, H.-k. Mao et al., “High P-T transformations of nitrogen to 170 GPa,” J. Chem. Phys. 126, 184505 (2007).10.1063/1.2723069
[8]	Y. A. Freiman, H. J. Jodl, and Y. Crespo, “Solid oxygen revisited,” Phys. Rep. 743, 1–55 (2018), a part of Special Issue: Solid oxygen revisited.10.1016/j.physrep.2018.03.003
[9]	J. B. Neaton and N. W. Ashcroft, “Low-energy linear structures in dense oxygen: Implications for the ɛ phase,” Phys. Rev. Lett. 88, 205503 (2002).10.1103/physrevlett.88.205503
[10]	H. Fujihisa, Y. Akahama, H. Kawamura, Y. Ohishi, O. Shimomura et al., “O8 cluster structure of the epsilon phase of solid oxygen,” Phys. Rev. Lett. 97, 085503 (2006).10.1103/physrevlett.97.085503
[11]	Y. Akahama and H. Kawamura, “High-pressure Raman spectroscopy of solid oxygen,” Phys. Rev. B 54, R15602–R15605 (1996).10.1103/physrevb.54.r15602
[12]	Y. Akahama, H. Fujihisa, N. Hirao, and Y. Ohishi, “Relation between O8 cluster shape and vibrational spectra in the ɛ-phase of solid oxygen,” Jpn. J. Appl. Phys. 58, 095502 (2019).10.7567/1347-4065/ab355a
[13]	D. Schiferl, D. T. Cromer, and R. L. Mills, “Structure of O2 at 5.5 GPa and 299 K,” Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 37, 1329–1332 (1981).10.1107/s0567740881005852
[14]	D. Schiferl, D. T. Cromer, L. A. Schwalbe, and R. L. Mills, “Structure of ‘orange’ 18O2 at 9.6 GPa and 297 K,” Acta Crystallogr., Sect. B: Struct. Sci. 39, 153–157 (1983).10.1107/s0108768183002219
[15]	L. F. Lundegaard, G. Weck, M. I. McMahon, S. Desgreniers, and P. Loubeyre, “Observation of an O8 molecular lattice in the epsilon phase of solid oxygen,” Nature 443, 201–204 (2006).10.1038/nature05174
[16]	G. W. Stinton, I. Loa, L. F. Lundegaard, and M. I. McMahon, “The crystal structures of δ and δ* nitrogen,” J. Chem. Phys. 131, 104511 (2009).10.1063/1.3204074
[17]	F. A. Gorelli, P. Dalladay-Simpson, G. Garbarino, M. Mezouar, J. Haines et al., “Structural evidence for the spin collapse in high pressure solid oxygen,” Phys. Rev. Lett. 135, 076101 (2025).10.1103/jvd7-v9h9
[18]	Y. Akahama, H. Kawamura, D. Häusermann, M. Hanfland, and O. Shimomura, “New high-pressure structural transition of oxygen at 96 GPa associated with metallization in a molecular solid,” Phys. Rev. Lett. 74, 4690–4693 (1995).10.1103/physrevlett.74.4690
[19]	S. Desgreniers, Y. K. Vohra, and A. L. Ruoff, “Optical response of very high density solid oxygen to 132 GPa,” J. Phys. Chem. 94, 1117–1122 (1990).10.1021/j100366a020
[20]	G. Weck, P. Loubeyre, and R. LeToullec, “Observation of structural transformations in metal oxygen,” Phys. Rev. Lett. 88, 035504 (2002).10.1103/physrevlett.88.035504
[21]	A. F. Goncharov, E. Gregoryanz, R. J. Hemley, and H.-k. Mao, “Molecular character of the metallic high-pressure phase of oxygen,” Phys. Rev. B 68, 100102 (2003).10.1103/physrevb.68.100102
[22]	K. Shimizu, K. Suhara, M. Ikumo, M. I. Eremets, and K. Amaya, “Superconductivity in oxygen,” Nature 393, 767–769 (1998).10.1038/31656
[23]	P. Dalladay-Simpson, B. Monserrat, L. Zhang, and F. Gorelli, “Distinct vibrational signatures and complex phase behavior in metallic oxygen,” Matter Radiat. Extremes 9, 028401 (2023).10.1063/5.0160060
[24]	D. Schiferl, D. T. Cromer, R. R. Ryan, A. C. Larson, R. LeSar et al., “Structure of N2 at 2.94 GPa and 300 K,” Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 39, 1151–1153 (1983).10.1107/s0108270183007726
[25]	M. Hanfland, M. Lorenzen, C. Wassilew-Reul, and F. Zontone, “Structures of molecular nitrogen at high pressures,” Rev. High Pressure Sci. Technol. 7, 787–789 (1998).10.4131/jshpreview.7.787
[26]	H. Olijnyk, “High pressure x-ray diffraction studies on solid N2 up to 43.9 GPa,” J. Chem. Phys. 93, 8968–8972 (1990).10.1063/1.459236
[27]	E. Gregoryanz, A. F. Goncharov, R. J. Hemley, and H.-k. Mao, “High-pressure amorphous nitrogen,” Phys. Rev. B 64, 052103 (2001).10.1103/physrevb.64.052103
[28]	M. I. Eremets, A. G. Gavriliuk, I. A. Trojan, D. A. Dzivenko, and R. Boehler, “Single-bonded cubic form of nitrogen,” Nat. Mater. 3, 558–563 (2004).10.1038/nmat1146
[29]	M. I. Eremets, A. G. Gavriliuk, and I. A. Trojan, “Single-crystalline polymeric nitrogen,” Appl. Phys. Lett. 90, 171904 (2007).10.1063/1.2731679
[30]	B. J. Baer and M. Nicol, “New phase of an oxygen-nitrogen alloy at high pressure and room temperature detected by Raman spectroscopy,” J. Phys. Chem. 93, 1683–1687 (1989).10.1021/j100342a003
[31]	B. J. Baer and M. Nicol, “High-pressure binary phase diagram of nitrogen-oxygen at 295 K determined by Raman spectroscopy,” J. Phys. Chem. 94, 1073–1078 (1990).10.1021/j100366a009
[32]	K. Damde and H. Jodl, “Mixtures of (N2)1−x:(O2)x at high pressures and low temperatures,” J. Low Temp. Phys. 111, 327–337 (1998).10.1023/a:1022279518366
[33]	M. Minenko, J. Kreutz, T. Hupprich, and H. J. Jodl, “Raman investigation of the N2–O2 binary system as a function of pressure and temperature,” ChemInform 35, 200429008 (2004).10.1002/chin.200429008
[34]	D. Sihachakr and P. Loubeyre, “N2/O2 mixtures under pressure: A structural study of the binary phase diagram at 295 K,” Phys. Rev. B 70, 134105 (2004).10.1103/physrevb.70.134105
[35]	Y. Akahama, T. Maekawa, T. Sugimoto, H. Fujihisa, N. Hirao et al., “High-pressure phase diagram of O2 and N2 binary system: Formation of kagome-lattice of O2,” J. Phys.: Conf. Ser. 500, 182001 (2014).10.1088/1742-6596/500/18/182001
[36]	Y. Akahama, D. Ishihara, H. Yamashita, H. Fujihisa, N. Hirao et al., “Phase stability and magnetic behavior of hexagonal phase of N2–O2 system with kagome lattice under high pressure and low temperature,” Phys. Rev. B 94, 064104 (2016).10.1103/physrevb.94.064104
[37]	K. Syassen, “Ruby under pressure,” High Pressure Res. 28, 75–126 (2008).10.1080/08957950802235640
[38]	Y. Akahama and H. Kawamura, “Pressure calibration of diamond anvil Raman gauge to 310 GPa,” J. Appl. Phys. 100, 043516 (2006).10.1063/1.2335683
[39]	O. L. Anderson, D. G. Isaak, and S. Yamamoto, “Anharmonicity and the equation of state for gold,” J. Appl. Phys. 65, 1534–1543 (1989).10.1063/1.342969
[40]	C. Prescher and V. B. Prakapenka, “DIOPTAS: A program for reduction of two-dimensional X-ray diffraction data and data exploration,” High Pressure Res. 35, 223–230 (2015).10.1080/08957959.2015.1059835
[41]	B. H. Toby and R. B. Von Dreele, “GSAS-II: The genesis of a modern open-source all purpose crystallography software package,” J. Appl. Crystallogr. 46, 544–549 (2013).10.1107/s0021889813003531
[42]	Y.-A. Peng, H.-Y. Wang, F.-H. Su, P. Wang, H.-A. Xu et al., “Synthesis of lutetium hydrides at high pressures,” Matter Radiat. Extremes 10, 017804 (2024).10.1063/5.0227283
[43]	R. Reichlin, D. Schiferl, S. Martin, C. Vanderborgh, and R. L. Mills, “Optical studies of nitrogen to 130 GPa,” Phys. Rev. Lett. 55, 1464–1467 (1985).10.1103/physrevlett.55.1464
[44]	A. F. Goncharov, E. Gregoryanz, H.-k. Mao, Z. Liu, and R. J. Hemley, “Optical evidence for a nonmolecular phase of nitrogen above 150 GPa,” Phys. Rev. Lett. 85, 1262–1265 (2000).10.1103/physrevlett.85.1262