Elasticity, strength, and refractive index of argon at high pressures

High-pressure Brillouin spectroscopy of polycrystalline argon, measured using two scattering angles (180^∘ and 70^∘), determines the isotropic elastic moduli, shear strength, equation of state, and refractive index of face-centered-cubic argon from 1.3 to 30 GPa at room temperature. The index of refraction $n=1.33--1.67$ over this pressure range. An Eulerian finite-strain analysis (Birch-Murnaghan equation of state) yields an isothermal bulk modulus and pressure derivative KT=15.1(±1.1) GPa and KT^'=5.4(±0.3) at 2 GPa. The resulting equation of state agrees well with previous x-ray diffraction measurements, illustrating the suitability of high-pressure Brillouin scattering for characterizing the elasticity and strength of polycrystalline materials.