The Avramov model of structural relaxation

Abstract The Avramov model, an entropy-based description of the effects of temperature and pressure on structural relaxation times, assumes separability of these two dependences. This implies that the fragility of glass-formers is independent of pressure. Herein we show that experimental results for polymethyltolylsiloxane are at odds with this assumption. By introducing a linear increase of the coordination number of the liquid state with pressure, the model can be modified, enabling good agreement with experiment to be achieved.