Frequency-dependent equation of state of fused silica to 10 GPa

Charles Meade and Raymond Jeanloz
Phys. Rev. B 35, 236 – Published 1 January 1987
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Abstract

Using a new technique for optically determining strain in the diamond cell, we have measured the static compression of fused silica and a Ca-Mg-Na glass to over 10 GPa. In our experiments, irreversible compaction of fused silica is precipitated by shear stresses above 10 GPa. For the Ca-Mg-Na glass we observe irreversible compaction beyond 8 GPa under hydrostatic loading. In both glasses we find that the bulk modulus increases sharply at high hydrostatic pressures (∼11 and 7 GPa, respectively). We show that this increase in bulk modulus can be explained in terms of the transition between relaxed and unrelaxed moduli that is observed at zero pressure, low temperatures, and higher frequencies. Our compression data, measured under quasistatic (∼104 Hz) conditions, are consistent with a wide range of acoustic absorption (∼1051010 Hz) and dielectric loss (103104 Hz) measurements in constraining the activation volume for this relaxation process to be V*=7.9±1.7 cm3/mol. We propose that the relaxation involves a change in the compression mechanism, from SiOSi bond bending to SiO bond compression induced either by low temperatures or by high pressure.

  • Received 25 August 1986

DOI:https://doi.org/10.1103/PhysRevB.35.236

©1987 American Physical Society

Authors & Affiliations

Charles Meade and Raymond Jeanloz

  • Department of Geology and Geophysics, University of California, Berkeley, California 94720

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Vol. 35, Iss. 1 — 1 January 1987

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