Journal
PHYSICS OF THE EARTH AND PLANETARY INTERIORS
Volume 172, Issue 3-4, Pages 235-240Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.pepi.2008.09.017
Keywords
Elasticity; Stishovite; High-pressure; Silica
Categories
Funding
- NSF
- C-DAC (Carnegie DOE Alliance Center)
- DOE [DE-AC02-10866]
- COMPRES [EAR 06-49658]
- Division Of Earth Sciences
- Directorate For Geosciences [0738510] Funding Source: National Science Foundation
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Brillouin scattering measurements on single-crystal stishovite, a high-pressure polymorph of SiO(2), were carried out to 22 GPa. Acoustic velocities in three 30-mu m thick crystal platelets of synthetic stishovite were measured in a forward symmetric scattering geometry, and the full set of elastic constants were retrieved to 12 GPa. The measured velocity data were fit to Christoffel's equation, yielding ambient-pressure elastic constants of C(11) = 455(1) GPa, C(33) = 762(2) GPa, C(12) = 199(2) GPa, C(13) = 192(2) GPa, C(44) = 258(1) GPa, and C(66) = 321(1) GPa. The elastic modulus (C(11) - C(12))/2 was observed to decrease with pressure, indicating acoustic mode softening, consistent with theoretical predications for the behavior of stishovite as it approaches the transition to the CaCl(2)-type phase. The bounds on the aggregate adiabatic bulk and shear moduli are K(s0) = 315(1) GPa, G(0) = 240(1) GPa for the Voigt bound, K(s0) = 301(1) GPa, G(0) = 216(1) GPa for the Reuss bound. Pressure derivatives of aggregate bulk and shear moduli were constrained to be (partial derivative K(s)/partial derivative P)(T0) = 4.34(16) and (partial derivative G/partial derivative P)(0) = 0.7(1) for the Reuss bound, and (partial derivative K(s)/partial derivative P)(T0) = 4.0(1) and (partial derivative G/partial derivative P)(0) = 1.1(1) for the Voigt-Reuss-Hill (VRH) average, respectively, by fitting the data to Eulerian finite strain equations. The volume compression curve obtained from our Brillouin measurement is in very good agreement with previous compression studies up to 50GPa. (c) 2008 Elsevier B.V. All rights reserved.
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