Thermodynamical scaling of the glass transition dynamics

Classification of glass-forming liquids based on the dramatic change in their properties upon approach to the glassy state is appealing, since this is the most conspicuous and often-studied aspect of the glass transition. Herein, we show that a generalized scaling, log (tau) proportional, variant T-1 V-gamma, where gamma is a material constant, yields superpositioning for ten glass formers, encompassing van der Waals molecules, associated liquids, and polymers. The exponent gamma reflects the degree to which volume governs the temperature and pressure dependence of the relaxation times.