Relationship between structural and secondary relaxation in glass formers: Ratio between glass transition temperature and activation energy

The relationship between structural and secondary dynamics is one of the most recently considered and possibly important issues of the dynamics in glass formers. One relation of interest is the ratio between the activation energy of the secondary relaxation and RT g, where T g is the glass transition temperature, and R is the gas constant. This relationship has been recently rationalized by the Coupling Model in terms of many-body dynamics and was applied to the intermolecular Johari-Goldstein secondary relaxation. This article investigates the pressure dependence of this ratio and attempts to verify the validity of the Coupling Model predictions under such conditions.