Dynamic heterogeneities in a supercooled diatomic molecular system

Dynamic heterogeneities in a supercooled system of diatomic molecules with an associated dipole moment have been investigated. To this end, three-time correlation functions have been evaluated. Correlations between molecular displacements performed during consecutive time intervals are apparent at low temperatures in the beta -relaxation regime, whereas they tend to disappear during the alpha -relaxation regime. These correlations maximize when the deviation from Gaussian dynamics takes a maximum, and they reveal the existence of different dynamic domains. Directionality of translational motions has also been studied. At low temperatures, and in the beta -relaxation zone, the molecular vector displacement in a given time interval has an important component in the opposite direction of the vector displacement corresponding to the initial time interval. The amplitudes associated with this quasi-oscillatory behavior become larger as the system is cooled. Dynamic heterogeneities in reorientation have been observed in the beta -relaxation regime, and it has been obtained that molecules that perform faster translational motions experience faster reorientational motions too. This effect increases as temperature decreases.