Elasticity of single‐crystal forsterite measured to 1700 K

TLDR: In this paper, the nine adiabatic elastic constants of single-crystal forsterite are reported for the temperature range 300-1700 K at ambient pressure, and the resulting Hill-averaged bulk and rigidity moduli Ks and G are lower at 1700 K than predicted by linear extrapolation of low-temperature data.

Abstract: Measurements of the nine adiabatic elastic constants of single-crystal forsterite are reported for the temperature range 300–1700 K at ambient pressure. The measured room temperature Cijs and their first temperature derivatives at ambient conditions are generally consistent with previous measurements, which were taken over a narrower temperature range. Slight nonlinear behavior is observed in the temperature dependence of the C11s, C22s, and C33s moduli. The resulting Hill-averaged bulk and rigidity moduli Ks and G are lower at 1700 K than predicted by linear extrapolation of low-temperature data. At 1700 K the new data give Ks = 103.8 ± 1.1 GPa and G = 61.3 ± 0.5 GPa. Isotropic elastic wave velocities have been calculated using the Hill averaging scheme over the range of temperatures measured. At T = 1700 K and ambient pressure we find vp = 7.79 ± 0.04 km s−1 and vs = 4.48 ± 0.03 km s−1. The parameter (∂lnvs/∂lnvp)P is near to 1.2 and independent of temperature. Calculations are presented for elastic properties and other parameters important for the equations of state and anharmonicity of forsterite. Recent high-temperature thermal expansion measurements on a forsterite specimen from the same boule are used in this analysis. Effects of uncertainties in high-temperature thermal expansion data on these parameters have been evaluated and are discussed.