Shock-synthesized glassy and solid silica: intermediates between four- and six-fold coordination

Abstract

Upon compression, many materials undergo major reconstructions of their structure and bonding, including increases in coordination of atoms and changes in bonding character. While transforming, the materials pass through intermediate states, which are often too transient to be captured and examined. Here we discuss the coordination change in silica as an example of a system where such interesting intermediate structural states have been quenched from shock-experiments. On the basis of these results we suggest a relation between the formation of one of these phases and the extension of the liquid–liquid transition boundary into the stability field of solid silica. We report Raman spectra of shock-retrieved vitreous silica which indicate different compression mechanisms for shock-generated amorphous silica and vitreous silica compressed at 300 K. Static recompression of shock-generated glass leads to an amorphous-crystal transition above 13 GPa.

Acknowledgements

This work was supported by NNSA Cooperative Agreement DE-FC88-01NV14049. Some material used in this study is based on work supported by the NASA/Goddard Award no. NNG04G107G, Division of Geological and Planetary Sciences, California Institute of Technology and NASA Grant NAG5-10198. S.N.L. is sponsored by a Director's Postdoctoral Fellowship at LANL. We are grateful for the invaluable support from the Trident laser facility and staff at LANL. Use of the HPCAT facility was supported by DOE-BES, DOE-NNSA, NSF, DOD-TACOM, and the W.M. Keck Foundation. Use of the APS was supported by the US Department of Energy, Basic Energy Sciences, Office of Energy Research under contract no. W-31-109-Eng-38. This work was partly performed at Los Alamos National Laboratory under the auspices of the US Department of Energy under contract no. W-7405-ENG-36.