Elasticity of single-crystal phase D (a dense hydrous magnesium silicate) by Brillouin spectroscopy

摘要

Phase D (Mg2Si2O6H2) is the only hydrous magnesium silicate, where all Si atoms are octahedrally coordinated. The single-crystal elastic constants of phase D have been measured by Brillouin spectroscopy at ambient conditions. The elastic constants C-11, C-33, C-44, C-12, C-13 and C-14, based on a trigonal unit cell, are 284.4 +/- 3.0, 339.4 +/- 9.1, 120.7 +/- 1.9, 89.4 +/- 4.2, 126.6 +/- 3.1 and - 4.7 +/- 1.4 GPa, respectively. The aggregate adiabatic bulk modulus, using the Voigt-Reuss-Hill (VRH) scheme, is 175.3 +/- 14.8 GPa and the shear modulus is 104.4 +/- 13.6 GPa. These data yield the compressional-wave velocity, V-p = 9.70 +/- 0.51 km/s. and the shear-wave velocity, V-s = 5.59 +/- 0.36 km/s, at ambient conditions. Thus, phase D is not only the most closely packed but the least compressible hydrous magnesium silicate known to date. (C) 2004 Elsevier Ltd. All rights reserved.