Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Experimental evidence for a phase transition in magnesium oxide at exoplanet pressures

Abstract

Magnesium oxide is an important component of the Earth’s mantle and has been extensively studied at pressures and temperatures relevant to Earth1. However, much less is known about the behaviour of this oxide under conditions likely to occur in extrasolar planets with masses up to 10 times that of Earth, termed super-Earths, where pressures can exceed 1,000 GPa (10 million atmospheres). Magnesium oxide is expected to change from a rocksalt crystal structure (B1) to a caesium chloride (B2) structure at pressures of about 400–600 GPa (refs 2, 3). Whereas no structural transformation was observed in static compression experiments up to 250 GPa (ref. 4), evidence for a solid–solid phase transition was obtained in shockwave experiments above 400 GPa and 9,000 K (ref. 5), albeit no structural measurements were made. As a result, the properties and the structure of MgO under conditions relevant to super-Earths and large planets are unknown. Here we present dynamic X-ray diffraction measurements of ramp-compressed magnesium oxide. We show that a solid–solid phase transition, consistent with a transformation to the B2 structure, occurs near 600 GPa. On further compression, this structure remains stable to 900 GPa. Our results provide an experimental benchmark to the equations of state and transition pressure of magnesium oxide, and may help constrain mantle viscosity and convection in the deep mantle of extrasolar super-Earths.

This is a preview of subscription content

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Experimental set-up for X-ray diffraction and ramp-compression at the OMEGA Laser Facility.
Figure 2: X-ray diffraction patterns of compressed MgO.
Figure 3: d-spacings and density versus stress.

References

  1. 1

    Duffy, T. S., Hemley, R. J. & Mao, H-k. Equation of state and shear strength at multimegabar pressures: Magnesium oxide to 227 GPa. Phys. Rev. Lett. 74, 1371–1374 (1995).

    Article  Google Scholar 

  2. 2

    Oganov, A. R., Gillan, M. J. & Price, G. D. Ab initio lattice dynamics and structural stability of MgO. J. Chem. Phys. 118, 10174–10182 (2003).

    Article  Google Scholar 

  3. 3

    Belonoshko, A. B., Arapan, S., Martonak, R. & Rosengren, A. MgO phase diagram from first principles in a wide pressure–temperature range. Phys. Rev. B 81, 054110 (2010).

    Article  Google Scholar 

  4. 4

    Dorfman, S. M., Prakapenka, V. B., Meng, Y. & Duffy, T. S. Intercomparison of pressure standards (Au, Pt, Mo, MgO, NaCl and Ne) to 2.5 Mbar. J. Geophys. Res. 117, B08210 (2012).

    Google Scholar 

  5. 5

    McWilliams, R. S. et al. Phase transformations and metallization of magnesium oxide at high pressure and temperature. Science 338, 1330–1333 (2012).

    Article  Google Scholar 

  6. 6

    Karato, S-i. Rheological structure of the mantle of a super-Earth: Some insights from mineral physics. Icarus 212, 14–23 (2011).

    Article  Google Scholar 

  7. 7

    Valencia, D., O’Connell, R. J. & Sasselov, D. Internal structure of massive terrestrial planets. Icarus 181, 545–554 (2006).

    Article  Google Scholar 

  8. 8

    Wagner, F. W., Tosi, N., Sohl, F., Rauer, H. & Spohn, T. Rocky super-Earth interiors. Structure and internal dynamics of CoRoT-7b and Kepler-10b. Astron. Astrophys. 541, A103 (2012).

    Article  Google Scholar 

  9. 9

    Swift, D. C. et al. Mass-radius relationships for exoplanets. Astrophys. J. 744, 59 (2012).

    Article  Google Scholar 

  10. 10

    Umemoto, K. & Wentzcovitch, R. M. Two-stage dissociation in MgSiO3 post-perovskite. Earth Planet. Sci. Lett. 311, 225–229 (2011).

    Article  Google Scholar 

  11. 11

    Tsuchiya, T. & Tsuchiya, J. Prediction of a hexagonal SiO2 phase affecting stabilities of MgSiO3 and CaSiO3 at multimegabar pressures. Proc. Natl Acad. Sci. USA 108, 1252–1255 (2011).

    Article  Google Scholar 

  12. 12

    Dewaele, A., Fiquet, G., Andrault, D. & Hausermann, D. P-V-T equation of state of periclase from synchrotron measurements. J. Geophys. Res. 105, 2869–2877 (2000).

    Article  Google Scholar 

  13. 13

    Strachan, A., Çagin, T. & Goddard, W. A. Phase diagram of MgO from density-functional theory and molecular-dynamics simulations. Phys. Rev. B 60, 15084–15093 (1999).

    Article  Google Scholar 

  14. 14

    Mehl, M. J., Cohen, R. E. & Krakauer, H. Linearized augmented plane wave electronic structure calculation for MgO and CaO. J. Geophys. Res. 93, 8009–8022 (1988).

    Article  Google Scholar 

  15. 15

    Drummond, N. & Ackland, G. Ab initio quasiharmonic equations of state for dynamically stabilized soft-mode materials. Phys. Rev. B 65, 184104–184104 (2002).

    Article  Google Scholar 

  16. 16

    Boehly, T. R. et al. Initial performance results of the OMEGA laser system. Opt. Commun. 133, 495–506 (1997).

    Article  Google Scholar 

  17. 17

    Rygg, J. R. et al. Powder diffraction from solids in the terapascal regime. Rev. Sci. Instrum. 83, 113904 (2012).

    Article  Google Scholar 

  18. 18

    Celliers, P. M. et al. Line-imaging velocimeter for shock diagnostics at the OMEGA laser facility. Rev. Sci. Instrum. 75, 4916–4929 (2004).

    Article  Google Scholar 

  19. 19

    Bradley, D. K. et al. Diamond at 800 GPa. Phys. Rev. Lett. 102, 075503 (2009).

    Article  Google Scholar 

  20. 20

    Maw, J. R. A characteristics code for analysis of isentropic compression experiments. AIP Conf. Proc. 706, 1217–1220 (2004).

    Article  Google Scholar 

  21. 21

    Rothman, S. D. & Maw, J. Characteristics analysis of isentropic compression experiments (ICE). J. Physique 134, 745–750 (2006).

    Google Scholar 

  22. 22

    Causà, M., Dovesi, R., Pisani, C. & Roetti, C. Electronic structure and stability of different crystal phases of magnesium oxide. Phys. Rev. B 33, 1308–1316 (1986).

    Article  Google Scholar 

  23. 23

    Zhang, L., Gong, Z. & Fei, Y. Shock-induced phase transitions in the MgO–FeO system to 200GPa. J. Phys. Chem. Solids 69, 2344–2348 (2008).

    Article  Google Scholar 

  24. 24

    Bukowinski, M. S. T. First principles equations of state of MgO and CaO. Geophys. Res. Lett. 12, 536–539 (1985).

    Article  Google Scholar 

  25. 25

    Marsh, S. LASL Shock Hugoniot Data (Univ. California Press, 1980).

    Google Scholar 

  26. 26

    Vassiliou, M. S. & Ahrens, T. J. Hugoniot equation of state of periclase to 200 GPa. Geophys. Res. Lett. 8, 729–732 (1981).

    Article  Google Scholar 

  27. 27

    Duffy, T. S. & Ahrens, T. J. Compressional sound velocity, equation of state, and constitutive response of shock-compressed magnesium oxide. J. Geophys. Res. 100, 529–542 (1995).

    Article  Google Scholar 

  28. 28

    Wu, Z. et al. Pressure-volume-temperature relations in MgO: An ultrahigh pressure-temperature scale for planetary sciences applications. J. Geophys. Res. 113, 1–12 (2008).

    Google Scholar 

  29. 29

    Bond, J. C., O’Brien, D. P. & Lauretta, D. S. The compositional diversity of extrasolar terrestrial planets. I. In situ simulations. Astrophys. J. 715, 1050–1070 (2010).

    Article  Google Scholar 

  30. 30

    van den Berg, A. P., Yuen, D. A., Beebe, G. L. & Christiansen, M. D. The dynamical impact of electronic thermal conductivity on deep mantle convection of exosolar planets. Phys. Earth Planet. Inter. 178, 136–154 (2010).

    Article  Google Scholar 

Download references

Acknowledgements

The authors thank S. Uhlich, W. Unites, T. Uphaus and R. Wallace for their assistance in target preparation and the operation staff at the OMEGA Laser Facility for supporting these experiments. F.C. is grateful to D. C. Swift for providing a tabular equation of state of MgO. The authors thank R. E. Cohen and M. J. Mehl for discussions and for making simulation results available. This work was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344. The research was supported by NNSA/DOE through the National Laser Users’ Facility Program under contracts DE-NA0000856 and DE-FG52-09NA29037. Part of this work was financially supported by the Laboratory Directed Research and Development program at LLNL (project number 12-SI-007).

Author information

Affiliations

Authors

Contributions

F.C. was the primary person who designed and performed the experiment, analysed the data and wrote the manuscript. R.F.S., J.H.E. and T.S.D assisted in the design and performance of the experiment and contributed to the manuscript. J.W. assisted in the design and performance of the experiment. J.R.R., A.L. and J.A.H. participated in the design of the experiment. G.W.C. participated in the design of the experiment and contributed to the manuscript. All of the authors discussed the results together and commented on drafts of the manuscript.

Corresponding author

Correspondence to F. Coppari.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 5216 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Coppari, F., Smith, R., Eggert, J. et al. Experimental evidence for a phase transition in magnesium oxide at exoplanet pressures. Nature Geosci 6, 926–929 (2013). https://doi.org/10.1038/ngeo1948

Download citation

Further reading

Search

Quick links