Dynamical and structural correlation in supercooled liquids: a molecular dynamics investigation of m-toluidine

Structural and dynamical properties of liquid and supercooled liquid m-toluidine are studied by molecular dynamics simulations. Approaching the liquid-glass transition, dynamical heterogeneities, a characteristic common to all supercooled glass formers, are observed. We prove the occurrence of strict correlation between these heterogeneities and the potential energy landscape of the system, expressed in terms of molecule-molecule interactions. A slowing down of the self-diffusive motion of the molecular centers of mass is observed for particular arrangements of pairs of H-bonded molecules. Previous studies on model systems provided evidence of the correlation between dynamical heterogeneities and potential energy landscape, described in terms of the inherent structure of the system. While in this last case the structure is viewed as a collective property of the system, in m-toluidine short-range interactions are sufficient to explain the dynamical behavior in a satisfactory way. This result agrees with the view, supported also by experimental observations, that m-toluidine can be considered as an ensemble of H-bonded subsystems weakly interacting among them.