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, $\log \left(\tau \right)\propto T^{-1}{V}^{-\gamma }$, 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.

• Received 9 December 2003

DOI:https://doi.org/10.1103/PhysRevE.69.062501