Femtosecond X-ray Diffraction of Laser-shocked Forsterite (Mg2SiO4) to 122 GPa

Kim, Donghoon; Tracy, Sally J.; Smith, Raymond F.; Gleason, Arianna E.; Bolme, Cindy A.; Prakapenka, Vitali B.; Appel, Karen; Speziable, Sergio; Wicks, June K.; Berryman, Eleanor J.; Han, Sirus K.; Schoelmerich, Markus O.; Lee, Hae Ja; Nagler, Bob; Cunningham, Eric F.; Akin, Minta C.; Asimow, Paul D.; Eggert, Jon H.; Duffy, Thomas S.
Issue date: November 2020
Cite as:
Kim, Donghoon, Tracy, Sally J., Smith, Raymond F., Gleason, Arianna E., Bolme, Cindy A., Prakapenka, Vitali B., Appel, Karen, Speziable, Sergio, Wicks, June K., Berryman, Eleanor J., Han, Sirus K., Schoelmerich, Markus O., Lee, Hae Ja, Nagler, Bob, Cunningham, Eric F., Akin, Minta C., Asimow, Paul D., Eggert, Jon H., & Duffy, Thomas S. (2020). Femtosecond X-ray Diffraction of Laser-shocked Forsterite (Mg2SiO4) to 122 GPa [Data set]. Princeton University. https://doi.org/10.34770/gg40-tc15
  author      = {Kim, Donghoon and
                Tracy, Sally J. and
                Smith, Raymond F. and
                Gleason, Arianna E. and
                Bolme, Cindy A. and
                Prakapenka, Vitali B. and
                Appel, Karen and
                Speziable, Sergio and
                Wicks, June K. and
                Berryman, Eleanor J. and
                Han, Sirus K. and
                Schoelmerich, Markus O. and
                Lee, Hae Ja and
                Nagler, Bob and
                Cunningham, Eric F. and
                Akin, Minta C. and
                Asimow, Paul D. and
                Eggert, Jon H. and
                Duffy, Thomas S.},
  title       = {{Femtosecond X-ray Diffraction of Laser-s
                hocked Forsterite (Mg2SiO4) to 122 GPa}},
  publisher   = {{Princeton University}},
  year        = 2020,
  url         = {https://doi.org/10.34770/gg40-tc15}

The behavior of forsterite, Mg2SiO4, under dynamic compression is of fundamental importance for understanding its phase transformations and high-pressure behavior. Here, we have carried out an in situ X-ray diffraction study of laser-shocked poly- and single-crystal forsterite (a-, b-, and c- orientations) from 19 to 122 GPa using the Matter in Extreme Conditions end-station of the Linac Coherent Light Source. Under laser-based shock loading, forsterite does not transform to the high-pressure equilibrium assemblage of MgSiO3 bridgmanite and MgO periclase, as was suggested previously. Instead, we observe forsterite and forsterite III, a metastable polymorph of Mg2SiO4, coexisting in a mixed-phase region from 33 to 75 GPa for both polycrystalline and single-crystal samples. Densities inferred from X-ray diffraction data are consistent with earlier gas-gun shock data. At higher stress, the behavior observed is sample-dependent. Polycrystalline samples undergo amorphization above 79 GPa. For [010]- and [001]-oriented crystals, a mixture of crystalline and amorphous material is observed to 108 GPa, whereas the [100]-oriented crystal adopts an unknown crystal structure at 122 GPa. The Q values of the first two sharp diffraction peaks of amorphous Mg2SiO4 show a similar trend with compression as those observed for MgSiO3 glass in both recent static and laser-compression experiments. Upon release to ambient pressure, all samples retain or revert to forsterite with evidence for amorphous material also present in some cases. This study demonstrates the utility of femtosecond free-electron laser X-ray sources for probing the time evolution of high-pressure silicates through the nanosecond-scale events of shock compression and release.

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1 Fo_shock_data_JGR.zip 7.72 MB