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

Here, magnesium oxide, an important component of the Earth’s mantle, has been extensively studied in the pressure and temperature range found within the Earth. However,much less is known about its behavior under conditions appropriate for newly-discovered super-Earth planets, where pressures can exceed 1000 GPa (10 Mbar). It is widely believed that MgO will follow the rocksalt (B1) to cesium chloride (B2) transformation pathway commonly found for many alkali halides, alkaline earth oxides and various other ionic compounds. Static compression experiments have determined the structure of MgO to 250 GPa but have been unable to reach pressures necessary to induce the predicted transformation, resulting in large uncertainties regarding its properties under conditions relevant to super-Earths and other large planets. Here we report new dynamic x-ray diffraction measurements of ramp-compressed MgO to 900 GPa.We report evidence for the B2 phase beginning near 600 GPa, remaining stable on further compression to 900 GPa, the highest pressure diffraction data ever collected.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Princeton Univ., Princeton, NJ (United States)
Publication Date:
Grant/Contract Number:
NA0002154
Type:
Accepted Manuscript
Journal Name:
Nature Geoscience
Additional Journal Information:
Journal Volume: 6; Journal Issue: 11; Journal ID: ISSN 1752-0894
Publisher:
Nature Publishing Group
Research Org:
Princeton Univ., NJ (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES
OSTI Identifier:
1337785

Coppari, F., Smith, R. F., Eggert, J. H., Wang, J., Rygg, J. R., Lazicki, A., Hawreliak, J. A., Collins, G. W., and Duffy, T. S.. Experimental evidence for a phase transition in magnesium oxide at exoplanet pressures. United States: N. p., Web. doi:10.1038/ngeo1948.
Coppari, F., Smith, R. F., Eggert, J. H., Wang, J., Rygg, J. R., Lazicki, A., Hawreliak, J. A., Collins, G. W., & Duffy, T. S.. Experimental evidence for a phase transition in magnesium oxide at exoplanet pressures. United States. doi:10.1038/ngeo1948.
Coppari, F., Smith, R. F., Eggert, J. H., Wang, J., Rygg, J. R., Lazicki, A., Hawreliak, J. A., Collins, G. W., and Duffy, T. S.. 2013. "Experimental evidence for a phase transition in magnesium oxide at exoplanet pressures". United States. doi:10.1038/ngeo1948. https://www.osti.gov/servlets/purl/1337785.
@article{osti_1337785,
title = {Experimental evidence for a phase transition in magnesium oxide at exoplanet pressures},
author = {Coppari, F. and Smith, R. F. and Eggert, J. H. and Wang, J. and Rygg, J. R. and Lazicki, A. and Hawreliak, J. A. and Collins, G. W. and Duffy, T. S.},
abstractNote = {Here, magnesium oxide, an important component of the Earth’s mantle, has been extensively studied in the pressure and temperature range found within the Earth. However,much less is known about its behavior under conditions appropriate for newly-discovered super-Earth planets, where pressures can exceed 1000 GPa (10 Mbar). It is widely believed that MgO will follow the rocksalt (B1) to cesium chloride (B2) transformation pathway commonly found for many alkali halides, alkaline earth oxides and various other ionic compounds. Static compression experiments have determined the structure of MgO to 250 GPa but have been unable to reach pressures necessary to induce the predicted transformation, resulting in large uncertainties regarding its properties under conditions relevant to super-Earths and other large planets. Here we report new dynamic x-ray diffraction measurements of ramp-compressed MgO to 900 GPa.We report evidence for the B2 phase beginning near 600 GPa, remaining stable on further compression to 900 GPa, the highest pressure diffraction data ever collected.},
doi = {10.1038/ngeo1948},
journal = {Nature Geoscience},
number = 11,
volume = 6,
place = {United States},
year = {2013},
month = {9}
}