# Experimental evidence for superionic water ice using shock compression

## Abstract

In stark contrast to common ice, Ih, water ice at planetary interior conditions has been predicted to become superionic with fast-diffusing (that is, liquid-like) hydrogen ions moving within a solid lattice of oxygen. Likely to constitute a large fraction of icy giant planets, this extraordinary phase has not been observed in the laboratory. Here, we report laser-driven shock-compression experiments on water ice VII. Using time-resolved optical pyrometry and laser velocimetry measurements as well as supporting density functional theory–molecular dynamics (DFT-MD) simulations, we document the shock equation of state of H2O to unprecedented extreme conditions and unravel thermodynamic signatures showing that ice melts near 5,000 K at 190 GPa. Optical reflectivity and absorption measurements also demonstrate the low electronic conductivity of ice, which, combined with previous measurements of the total electrical conductivity under reverberating shock compression, provides experimental evidence for superionic conduction in water ice at planetary interior conditions, verifying a 30-year-old prediction.

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## References

1. 1.

Dunaeva, A. N., Antsyshkin, D. V. & Kuskov, O. L. Phase diagram of H2O: thermodynamic functions of the phase transitions of high-pressure ices. Sol. Syst. Res. 44, 222–243 (2010).

2. 2.

Bartels-Rausch, T. et al. Ice structures, patterns, and processes: a view across the icefields. Rev. Mod. Phys. 84, 885–944 (2012).

3. 3.

Goncharov, A. F., Struzhkin, V. V., Somayazulu, M. S., Hemley, R. J. & Mao, H. K. Compression of ice to 210 gigapascals: infrared evidence for a symmetric hydrogen-bonded phase. Science 273, 218–220 (1996).

4. 4.

Loubeyre, P., LeToullec, R., Wolanin, E., Hanfland, M. & Hausermann, D. Modulated phases and proton centring in ice observed by X-ray diffraction up to 170 GPa. Nature 397, 503–506 (1999).

5. 5.

Demontis, P., LeSar, R. & Klein, M. L. New high-pressure phases of ice. Phys. Rev. Lett. 60, 2284–2287 (1988).

6. 6.

Benoit, M., Bernasconi, M., Focher, P. & Parrinello, M. New high-pressure phase of ice. Phys. Rev. Lett. 76, 2934–2936 (1996).

7. 7.

Cavazzoni, C. et al. Superionic and metallic states of water and ammonia at giant planet conditions. Science 283, 44–46 (1999).

8. 8.

Goldman, N., Fried, L., Kuo, I.-F. & Mundy, C. Bonding in the superionic phase of water. Phys. Rev. Lett. 94, 217801 (2005).

9. 9.

Schwegler, E., Sharma, M., Gygi, F. & Galli, G. Melting of ice under pressure. Proc. Natl Acad. Sci. USA 105, 14779–14783 (2008).

10. 10.

French, M., Mattsson, T., Nettelmann, N. & Redmer, R. Equation of state and phase diagram of water at ultrahigh pressures as in planetary interiors. Phys. Rev. B 79, 054107 (2009).

11. 11.

Redmer, R., Mattsson, T. R., Nettelmann, N. & French, M. The phase diagram of water and the magnetic fields of Uranus and Neptune. Icarus 211, 798–803 (2011).

12. 12.

Mattsson, T. R. & Desjarlais, M. P. Phase diagram and electrical conductivity of high energy-density water from density functional theory. Phys. Rev. Lett. 97, 017801 (2006).

13. 13.

Wilson, H. F., Wong, M. L. & Militzer, B. Superionic to superionic phase change in water: consequences for the interiors of Uranus and Neptune. Phys. Rev. Lett. 110, 151102 (2013).

14. 14.

Sun, J., Clark, B. K., Torquato, S. & Car, R. The phase diagram of high-pressure superionic ice. Nat. Commun. 6, 8156 (2015).

15. 15.

French, M., Desjarlais, M. P. & Redmer, R. Ab-initio calculation of thermodynamic potentials and entropies for superionic water. Phys. Rev. E 93, 022140 (2016).

16. 16.

Hernandez, J.-a & Caracas, R. Superionic-superionic phase transitions in body-centered cubic H2O ice. Phys. Rev. Lett. 117, 135503 (2016).

17. 17.

French, M., Mattsson, T. & Redmer, R. Diffusion and electrical conductivity in water at ultrahigh pressures. Phys. Rev. B 82, 174108 (2010).

18. 18.

French, M., Hamel, S. & Redmer, R. Dynamical screening and ionic conductivity in water from ab initio simulations. Phys. Rev. Lett. 107, 185901 (2011).

19. 19.

Goldman, N. et al. Ab initio simulation of the equation of state and kinetics of shocked water. J. Chem. Phys. 130, 124517 (2009).

20. 20.

Datchi, F., Loubeyre, P. & LeToullec, R. Extended and accurate determination of the melting curves of argon, helium, ice (H2O), and hydrogen (H2). Phys. Rev. B 61, 6535–6546 (2000).

21. 21.

Dubrovinskaia, N. & Dubrovinsky, L. Whole-cell heater for the diamond anvil cell. Rev. Sci. Instrum. 74, 3433–3437 (2003).

22. 22.

Frank, M. R. M., Fei, Y. & Hu, J. Constraining the equation of state of fluid H2O to 80 GPa using the melting curve, bulk modulus, and thermal expansivity of ice VII. Geochim. Cosmochim. Acta 68, 2781–2790 (2004).

23. 23.

Schwager, B., Chudinovskikh, L., Gavriliuk, A. & Boehler, R. Melting curve of H2O to 90 GPa measured in a laser-heated diamond cell. J. Phys. Condens. Matter 16, S1177–S1179 (2004).

24. 24.

Lin, J.-F. et al. Melting behavior of H2O at high pressures and temperatures. Geophys. Res. Lett. 32, L11306 (2005).

25. 25.

Goncharov, A. et al. Dynamic ionization of water under extreme conditions. Phys. Rev. Lett. 94, 125508 (2005).

26. 26.

Ahart, M., Karandikar, A., Gramsch, S., Boehler, R. & Hemley, R. J. High P-T Brillouin scattering study of H2O melting to 26 GPa. High Press. Res. 34, 327–336 (2014).

27. 27.

Kimura, T., Kuwayama, Y. & Yagi, T. Melting temperatures of H2O up to 72 GPa measured in a diamond anvil cell using CO2 laser heating technique. J. Chem. Phys. 140, 074501 (2014).

28. 28.

Sugimura, E. et al. Experimental evidence of superionic conduction in H2O ice. J. Chem. Phys. 137, 194505 (2012).

29. 29.

Kormer, S. B., Yushko, K. & Krishkevich, G. Phase transformation of water into ice VII by shock compression. Sov. Phys. JETP 27, 879–881 (1968).

30. 30.

Holmes, N., Nellis, W., Graham, W. & Walrafen, G. Spontaneous Raman scattering from shocked water. Phys. Rev. Lett. 55, 2433–2436 (1985).

31. 31.

Lyzenga, G. A. The temperature of shock-compressed water. J. Chem. Phys. 76, 6282 (1982).

32. 32.

Koenig, M. et al. High pressures generated by laser driven shocks: applications to planetary physics. Nucl. Fusion 44, S208–S214 (2004).

33. 33.

Peng, X., Liu, F., Zhang, S., Zhang, M. & Jing, F. The C V for calculating the shock temperatures of water below 80 GPa. Sci. China Phys. Mech. Astron. 54, 1443–1446 (2011).

34. 34.

Celliers, P. M. et al. Electronic conduction in shock-compressed water. Phys. Plasmas 11, L41 (2004).

35. 35.

Knudson, M. et al. Probing the interiors of the ice giants: shock compression of water to 700 GPa and 3.8 g/cm3. Phys. Rev. Lett. 108, 091102 (2012).

36. 36.

Kimura, T. et al. P-ρ-T measurements of H2O up to 260 GPa under laser-driven shock loading. J. Chem. Phys. 142, 164504 (2015).

37. 37.

Yuknavech, M. M. Memorandum Report. No. 1563 (Technical Report, Ballistic Research Laboratories, Aberdeen Proving Ground, MD, 1964).

38. 38.

Hamann, S. D. & Linton, M. Electrical conductivity of water in shock compression. Trans. Faraday Soc. 62, 2234–2241 (1966).

39. 39.

Mitchell, A. C. & Nellis, W. J. Equation of state and electrical conductivity of water and ammonia shocked to the 100 GPa (1 Mbar) pressure range. J. Chem. Phys. 76, 6273–6281 (1982).

40. 40.

Yakushev, V. V., Postnov, V. I., Fortov, V. E. & Yakysheva, T. I. Electrical conductivity of water during quasi-isentropic compression to 130 GPa. J. Exp. Theor. Phys. 90, 617–622 (2000).

41. 41.

Chau, R., Mitchell, A. C., Minich, R. W. & Nellis, W. J. Electrical conductivity of water compressed dynamically to pressures of 70–180 GPa (0.7–1.8 Mbar). J. Chem. Phys. 114, 1361 (2001).

42. 42.

Zha, C.-S., Hemley, R. J., Gramsch, S. A., Mao, H.-K. & Bassett, W. A. Optical study of H2O ice to 120 GPa: dielectric function, molecular polarizability, and equation of state. J. Chem. Phys. 126, 074506 (2007).

43. 43.

Lin, J.-F., Schwegler, E. & Yoo, C.-S. in Earths Deep Water Cycle (eds Jacobsen, S. D. & van der Lee, S.) Vol. 168, 159–169 (American Geophysical Union, Washington DC, 2006).

44. 44.

Goncharov, A. F. & Crowhurst, J. Proton delocalization under extreme conditions of high pressure and temperature. Phase Transitions 80, 1051–1072 (2007).

45. 45.

Stanley, S. & Bloxham, J. Convective-region geometry as the cause of Uranus’ and Neptune’s unusual magnetic fields. Nature 428, 151–153 (2004).

46. 46.

Nettelmann, N., Helled, R., Fortney, J. & Redmer, R. New indication for a dichotomy in the interior structure of Uranus and Neptune from the application of modified shape and rotation data. Planet. Space Sci. 77, 143–151 (2013).

47. 47.

Kirpichnikova, L. F., Urusovskaya, A. A. & Mozgovoi, V. I. Superplasticity of CsHSO4 crystals in the superionic phase. JETP Lett. 62, 638–641 (1995).

48. 48.

Tian, B. Y. & Stanley, S. Interior structure of water planets: implications for their dynamo source regions. Astrophys. J. 768, 156 (2013).

49. 49.

Zel’dovich, Y. B., Kormer, S. B., Sinitsyn, M. V. & Yushko, K. B. A study of the optical properties of transparent materials under high pressure. Sov. Phys. Dokl. 6, 494–496 (1961).

50. 50.

Kormer, S. B. Optical study of the characteristics of shock condensed dielectrics. Sov. Phys. Usp. 11, 229–254 (1968).

51. 51.

Chervin, J. C., Canny, B. & Mancinelli, M. Ruby-spheres as pressure gauge for optically transparent high pressure cells. High Press. Res. 21, 305–314 (2001).

52. 52.

Dewaele, A., Eggert, J. H., Loubeyre, P. & Le Toullec, R. Measurement of refractive index and equation of state in dense He, H2, H2O, and Ne under high pressure in a diamond anvil cell. Phys. Rev. B 67, 094112 (2003).

53. 53.

Bezacier, L. et al. Equations of state of ice VI and ice VII at high pressure and high temperature. J. Chem. Phys. 141, 104505 (2014).

54. 54.

Jeanloz, R. et al. Achieving high-density states through shock-wave loading of precompressed samples. Proc. Natl Acad. Sci. USA 104, 9172–9177 (2007).

55. 55.

Loubeyre, P. et al. Coupling static and dynamic compressions: first measurements in dense hydrogen. High Press. Res. 24, 25–31 (2004).

56. 56.

Lee, K. K. M. et al. Laser-driven shock experiments on precompressed water: implications for “icy” giant planets. J. Chem. Phys. 125, 014701 (2006).

57. 57.

Loubeyre, P. et al. Extended data set for the equation of state of warm dense hydrogen isotopes. Phys. Rev. B 86, 144115 (2012).

58. 58.

Eggert, J. et al. Hugoniot data for helium in the ionization regime. Phys. Rev. Lett. 100, 124503 (2008).

59. 59.

Celliers, P. M. et al. Insulator-to-conducting transition in dense fluid helium. Phys. Rev. Lett. 104, 184503 (2010).

60. 60.

Brygoo, S. et al. Analysis of laser shock experiments on precompressed samples using a quartz reference and application to warm dense hydrogen and helium. J. Appl. Phys. 118, 195901 (2015).

61. 61.

Millot, M. et al. Shock compression of stishovite and melting of silica at planetary interior conditions. Science 347, 418–420 (2015).

62. 62.

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

63. 63.

Miller, J. E. et al. Streaked optical pyrometer system for laser-driven shock-wave experiments on OMEGA. Rev. Sci. Instrum. 78, 034903 (2007).

64. 64.

Gregor, M. C. et al. Absolute calibration of the OMEGA streaked optical pyrometer for temperature measurements of compressed materials. Rev. Sci. Instrum. 87, 114903 (2016).

65. 65.

French, M. & Redmer, R. Construction of a thermodynamic potential for the water ices VII and X. Phys. Rev. B 91, 014308 (2015).

66. 66.

Berens, P. H., Mackay, D. H. J., White, G. M. & Wilson, K. R. Thermodynamics and quantum corrections from molecular dynamics for liquid water. J. Chem. Phys. 79, 2375 (1983).

67. 67.

French, M. & Redmer, R. Estimating the quantum effects from molecular vibrations of water under high pressures and temperatures. J. Phys. Condens. Matter 21, 375101 (2009).

68. 68.

Celliers, P. M., Collins, G. W., Hicks, D. G. & Eggert, J. H. Systematic uncertainties in shock-wave impedance-match analysis and the high-pressure equation of state of Al. J. Appl. Phys. 98, 113529 (2005).

69. 69.

Hicks, D. G. et al. Shock compression of quartz in the high-pressure fluid regime. Phys. Plasmas 12, 082702 (2005).

70. 70.

Desjarlais, M. P., Knudson, M. D. & Cochrane, K. R. Extension of the Hugoniot and analytical release model of α-quartz to 0.2–3 TPa. J. Appl. Phys. 122, 035903 (2017).

71. 71.

Hicks, D. G. et al. Dissociation of liquid silica at high pressures and temperatures. Phys. Rev. Lett. 97, 025502 (2006).

72. 72.

Millot, M. Identifying and discriminating phase transitions along decaying shocks with line imaging Doppler interferometric velocimetry and streaked optical pyrometry. Phys. Plasmas 23, 014503 (2016).

73. 73.

Larsen, J. T. & Lane, S. M. HYADES—a plasma hydrodynamics code for dense plasma studies. J. Quant. Spectrosc. Radiat. Transf. 51, 179–186 (1994).

74. 74.

Fratanduono, D. E. et al. Index of refraction of shock-released materials. J. Appl. Phys. 110, 083509 (2011).

## Acknowledgements

We gratefully acknowledge S. Uhlich, A. Correa Barrios, C. Davis, J. Emig, E. Folsom, R. Posadas Soriano, T. Uphaus and W. Unites for target preparation, the Omega Laser Facility management, staff and support crew for excellent shot and diagnostic support with special thanks to C. Sorce, A. Sorce and J. Kendrick, discussions with S. Brygoo, R. Chau, Z. Geballe, D. Hicks, P. Loubeyre and P. Sterne, and P. Loubeyre for re-analysing XRD data. Prepared by Lawrence Livermore National Laboratory (LLNL) under contract DE-AC52-07NA27344. Omega shots were allocated by the Laboratory Basic Science program of the Laboratory for Laser Energetics at the University of Rochester, NY. Extensive computational support was provided by the LLNL Computing facility. Partial support was provided by LLNL LDRD program 17-ERD-085, the US Department of Energy through the joint FES/NNSA HEDLP program, the University of California, including UC Berkeley’s Miller Institute for Basic Research in Science, the National Science Foundation (#PHY11-25915) and NASA (#NNH12AU44I).

## Author information

Authors

### Contributions

M.M. designed the project, prepared the pre-compressed cells, fielded the laser experiments, analysed the data and wrote the manuscript. J.R.R. was the principal investigator of the Omega campaign. S.H. performed DFT–MD simulations. P.M.C., J.H.E., J.R.R., G.W.C. and R.J. developed the laser DAC platform and associated analytical methods. J.R.R., D.E.F., F.C. and D.C.S. contributed to the data analysis. All authors discussed the data and commented on the manuscript.

### Corresponding author

Correspondence to Marius Millot.

## Ethics declarations

### Competing interests

The authors declare no competing financial interests.

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## Supplementary information

### Supplementary Information

I. Data analysis methods, II. Optical properties and electrical conductivity, III. Molecular dynamics simulations, IV. Models, simulations and previous experiment, V. Superionic water in planetary interiors and dynamo scaling

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Millot, M., Hamel, S., Rygg, J.R. et al. Experimental evidence for superionic water ice using shock compression. Nature Phys 14, 297–302 (2018). https://doi.org/10.1038/s41567-017-0017-4

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