Effect of entropy on the dynamics of supercooled liquids: new results from high pressure data

We show that for arbitrary thermodynamic conditions, master curves of the entropy are obtained by expressing S(T, V) as a function of TV γ G , where T is temperature, V specific volume and γG the thermodynamic Grüneisen parameter. A similar scaling is known for structural relaxation times, τ = ℑ (TV γ); however, we find γG < γ. We show herein that this inequality reflects contributions to S(T, V) from processes, such as vibrations and secondary relaxations, that do not directly influence the supercooled dynamics. An approximate method is proposed to remove these contributions, S 0, yielding the relationship τ = ℑ1(S − S 0).