Thermodynamic scaling of vibrational dynamics and relaxation.

We investigate by thorough molecular dynamics simulations the thermodynamic scaling (TS) of a polymer melt. Two distinct models, with strong and weak virial-energy correlations, are considered. Both evidence the joint TS with the same characteristic exponent γ of the fast mobility-the mean square amplitude of the picosecond rattling motion inside the cage-and the much slower structural relaxation and chain reorientation.