Figure 4: Time-dependent autocorrelation function of the unit C–N vectors.

The autocorrelation function has been computed averaging over the microcanonical ensemble sampled by constant number of particles, volume and energy (NVE) first-principles MD simulations performed at four different energies corresponding to average temperatures of 100, 200, 300 and 400 K. In the inset log τ₁ vs is shown, together with the linear fitting from which the rotational reorientation activation energy is obtained.