TEMPERATURE VARIATION OF ELASTIC CONSTANTS OF SINGLE-CRYSTAL FORSTERITE BETWEEN -190° AND 400°C

Abstract

Elastic constants of forsterite Mg₂SiO₄ were measured by the rectangular parallelepiped resonance (RPR) method at temperatures between -190° and 400°C. Elastic constant C_ij(Mbar) and their temperature derivatives ∂C_ij/∂T (kbar/deg) are:
The adiabatic bulk modulus Ks=1.292Mbar (25°C) and its temperature derivatives ∂Ks/∂T=-0.160kbar/deg (20°-400°C) are obtained by the Voigt-Reuss-Hill scheme.
In the temperature range from 100 to 1000K, the Gruneisen constant calculated from the measured bulk modulus is virtually constant at 1.1±0.1, while the Gruneisen-Anderson parameter δs, defined as -(∂ In Ks/∂T)/α(α: the coefficient of volume thermal expansion), decreases with increase of temperature, but tends to approach a constant value of 4.0±0.1 above 500K.