High-pressure viscoelastic properties and equation of state of liquids derived from Brillouin data

Brillouin scattering in an organic glass-forming liquid up to a pressure of 12 GPa is reported. The onset of the unrelaxed regime is indicated by a distinct maximum in the acoustic attenuation at a pressure P_α, above which weak shear modes are resolved. Sound velocity data are fitted in a self-consistent way which accounts for relaxation by combining the ``universal'' Vinet equation of state with an expression for the dynamical modulus. This analysis yields the pressure dependences of the relaxed and unrelaxed moduli, relaxation time, and density over the pressure range studied.