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.

  • Letter
  • Published:

Transparent dense sodium

Abstract

Under pressure, metals exhibit increasingly shorter interatomic distances. Intuitively, this response is expected to be accompanied by an increase in the widths of the valence and conduction bands and hence a more pronounced free-electron-like behaviour. But at the densities that can now be achieved experimentally, compression can be so substantial that core electrons overlap. This effect dramatically alters electronic properties from those typically associated with simple free-electron metals such as lithium (Li; refs 1–3) and sodium (Na; refs 4, 5), leading in turn to structurally complex phases6,7,8 and superconductivity with a high critical temperature9,10,11. But the most intriguing prediction—that the seemingly simple metals Li (ref. 1) and Na (ref. 4) will transform under pressure into insulating states, owing to pairing of alkali atoms—has yet to be experimentally confirmed. Here we report experimental observations of a pressure-induced transformation of Na into an optically transparent phase at 200 GPa (corresponding to 5.0-fold compression). Experimental and computational data identify the new phase as a wide bandgap dielectric with a six-coordinated, highly distorted double-hexagonal close-packed structure. We attribute the emergence of this dense insulating state not to atom pairing, but to pd hybridizations of valence electrons and their repulsion by core electrons into the lattice interstices. We expect that such insulating states may also form in other elements and compounds when compression is sufficiently strong that atomic cores start to overlap strongly.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Raman spectra of sodium.
Figure 2: Phase transformations in Na at megabar pressures.
Figure 3: Enthalpy curves (relative to f.c.c.) as a function of pressure for cI16, CsIV, α-Ga, oP8, tI19 and hP4 structures of Na.
Figure 4: Structural and electronic properties of Na-hP4.

Similar content being viewed by others

References

  1. Neaton, J. B. & Ashcroft, N. W. Pairing in dense lithium. Nature 400, 141–144 (1999)

    Article  CAS  ADS  Google Scholar 

  2. Tamblyn, I., Raty, J. Y. & Bonev, S. A. Tetrahedral clustering in molten lithium under pressure. Phys. Rev. Lett. 101, 075703 (2008)

    Article  ADS  Google Scholar 

  3. Ma, Y., Oganov, A. R. & Xie, Y. High pressure structures of lithium, potassium, rubidium predicted by ab initio evolutionary algorithm. Phys. Rev. B 78, 014102 (2008)

    Article  ADS  Google Scholar 

  4. Neaton, J. B. & Ashcroft, N. W. On the constitution of sodium at higher densities. Phys. Rev. Lett. 86, 2830–2833 (2001)

    Article  CAS  ADS  Google Scholar 

  5. Raty, J. Y., Schwegler, E. & Bonev, S. A. Electronic and structural transitions in dense liquid sodium. Nature 449, 448–451 (2007)

    Article  CAS  ADS  Google Scholar 

  6. Hanfland, M., Syassen, K., Christensen, N. E. & Novikov, D. L. New high-pressure phases of lithium. Nature 408, 174–178 (2000)

    Article  CAS  ADS  Google Scholar 

  7. Hanfland, M., Syassen, K., Loa, L., Christensen, N. E. & Novikov, D. L. Na at megabar pressures. Poster at 2002 High Pressure Gordon Conference (2002)

  8. Gregoryanz, E. et al. Structural diversity of sodium. Science 320, 1054–1057 (2008)

    Article  CAS  ADS  Google Scholar 

  9. Shimizu, K., Ishikawa, H., Takao, D., Yagi, T. & Amaya, K. Superconductivity in compressed lithium at 20 K. Nature 419, 597–599 (2002)

    Article  CAS  ADS  Google Scholar 

  10. Struzhkin, V. V., Eremets, M. I., Gan, W., Mao, H. K. & Hemley, R. J. Superconductivity in dense lithium. Science 298, 1213–1215 (2002)

    Article  CAS  ADS  Google Scholar 

  11. Deemyad, S. & Schilling, J. S. Superconducting phase diagram of Li metal in nearly hydrostatic pressures up to 67 GPa. Phys. Rev. Lett. 91, 167001 (2003)

    Article  ADS  Google Scholar 

  12. Hanfland, M., Loa, I. & Syassen, K. Sodium under pressure: bcc to fcc structural transition and pressure-volume relation to 100 GPa. Phys. Rev. B 65, 184109 (2002)

    Article  ADS  Google Scholar 

  13. Gregoryanz, E., Degtyareva, O., Somayazulu, M., Hemley, R. J. & Mao, H. K. Melting of dense sodium. Phys. Rev. Lett. 94, 185502 (2005)

    Article  ADS  Google Scholar 

  14. Christensen, N. E. & Novikov, D. L. High-pressure phases of the light alkali metals. Solid State Commun. 119, 477–490 (2001)

    Article  CAS  ADS  Google Scholar 

  15. McMahon, M. I. et al. Structure of sodium above 100 GPa by single-crystal x-ray diffraction. Proc. Natl Acad. Sci. USA 104, 17297–17299 (2007)

    Article  CAS  ADS  Google Scholar 

  16. Glass, C. W., Oganov, A. R. & Hansen, N. USPEX—Evolutionary crystal structure prediction. Comput. Phys. Commun. 175, 713–720 (2006)

    Article  CAS  ADS  Google Scholar 

  17. Oganov, A. R. & Glass, C. W. Crystal structure prediction using ab initio evolutionary techniques: Principles and applications. J. Chem. Phys. 124, 244704 (2006)

    Article  ADS  Google Scholar 

  18. Oganov, A. R., Glass, C. W. & Ono, S. High-pressure phases of CaCO3: Crystal structure prediction and experiment. Earth Planet. Sci. Lett. 241, 95–103 (2006)

    Article  CAS  ADS  Google Scholar 

  19. Ma, Y., Oganov, A. R. & Glass, C. W. Structure of the metallic ζ-phase of oxygen and isosymmetric nature of the ε-ζ phase transition: Ab initio simulations. Phys. Rev. B 76, 064101 (2007)

    Article  ADS  Google Scholar 

  20. Shishkin, M. & Kresse, G. Self-consistent GW calculations for semiconductors and insulators. Phys. Rev. B 75, 235102 (2007)

    Article  ADS  Google Scholar 

  21. Leger, J. M. & Haines, J. Crystal chemistry of the AX2 compounds under pressure. Eur. J. Solid State Inorg. Chem. 34, 785–796 (1997)

    CAS  Google Scholar 

  22. Dye, J. L. Electrides: From 1D Heisenberg chains to 2D pseudo-metals. Inorg. Chem. 36, 3816–3826 (1997)

    Article  CAS  Google Scholar 

  23. Eremets, M. I. Megabar high-pressure cells for Raman measurements. J. Raman Spectrosc. 34, 515–518 (2003)

    Article  CAS  ADS  Google Scholar 

  24. Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996)

    Article  CAS  ADS  Google Scholar 

  25. Blöchl, P. E. Projector augmented-wave method. Phys. Rev. B 50, 17953–17979 (1994)

    Article  ADS  Google Scholar 

  26. Kresse, G. & Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 59, 1758–1775 (1999)

    Article  CAS  ADS  Google Scholar 

  27. Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996)

    Article  CAS  ADS  Google Scholar 

  28. Gonze, X. et al. First-principles computation of material properties: The ABINIT software project. Comput. Mater. Sci. 25, 478–492 (2002); 〈http://www.abinit.org/

    Article  Google Scholar 

Download references

Acknowledgements

We thank the Swiss National Science Foundation (grants 200021-111847/1 and 200021-116219), CSCS and ETH Zurich for the use of supercomputers. Parts of the calculations were performed on the Skif supercomputer (Moscow State University, Russia) and at the Joint Supercomputer Centre of the Russian Academy of Sciences (Moscow). We acknowledge partial support from DFG (grants Er 539/1/2-1) and the China 973 Program (no. 2005CB724400). Part of the experimental work was performed at GeoSoilEnviroCARS (Sector 13), Advanced Photon Source (APS), Argonne National Laboratory.

Author Contributions Y.M. proposed the research and predicted the new structures. Y.M., Y.X. and A.R.O. did the calculations. M.E., I.T., S.M. and V.P. performed the experiments. Y.M., A.R.O. and M.E. contributed substantially to data interpretation and wrote the paper. A.L. wrote the latest version of the structure prediction code, and M.V. helped in data analysis. Y.M, M.E. and A.R.O contributed equally to this paper.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Yanming Ma.

Supplementary information

Supplementary Figures

This file contains Supplementary Figures 1-10 with Legends (PDF 1413 kb)

PowerPoint slides

Rights and permissions

Reprints and permissions

About this article

Cite this article

Ma, Y., Eremets, M., Oganov, A. et al. Transparent dense sodium. Nature 458, 182–185 (2009). https://doi.org/10.1038/nature07786

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature07786

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing