High-pressure yield strength of rocksalt structures using quartz Raman piezometry |
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Authors: | Bruno Reynard Razvan Caracas Hervé Cardon Gilles Montagnac Sébastien Merkel |
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Institution: | 1. Université de Lyon, École normale supérieure de Lyon, Université Claude-Bernard Lyon-1, CNRS UMR5276, 46, allée d’Italie, 69007 Lyon, France;2. Université de Lille, CNRS, INRA, ENSCL, UMR 8207, UMET, Unité Matériaux et Transformations, 59000 Lille, France |
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Abstract: | The Raman frequencies of quartz are used to evaluate deviatoric stresses in rocksalt-structure media in diamond-anvil cell experiments to pressures up to 20 GPa. The piezospectroscopic effect in quartz is modeled by first-principles calculations. Non-hydrostatic stresses measured in halogen salts give yield strength estimates of 3 GPa in the B1 structure (NaCl), and 4.5 GPa for the B2 structure (KCl and KBr). Raman measurements in MgO show that the yield strength is reached at around 6 ± 1 GPa. Measurements on quartz alone indicate similar yield strength. The estimated yield strength in MgO is thus likely a lower bound, in consistency with former radial X-ray diffraction measurements that gave a yield strength of 8 ± 1 GPa, and lower-pressure large-volume press experiments indicating a yield strength of 6 GPa at 5 GPa. Former values of the yield strength below 2 GPa determined by pressure gradient measurements were underestimated due to unverified assumptions in boundary conditions. The yield strength increases with increasing coordination of ionic solids, likely contributing to increase viscosity at phase transitions near the upper–lower mantle boundary. |
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Keywords: | Corresponding author High pressure Yield strength Halides Oxides |
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