Structural and dynamical heterogeneity in a glass-forming liquid

y We use the "isoconfigurational ensemble" [Phys. Rev. Lett. 93, 135701 (2004)] to analyze both dynamical and structural properties in simulations of a glass-forming molecular liquid. We show that spatially correlated clusters of low-potential-energy molecules are observable on the time scale of structural relaxation, despite the absence of spatial correlations of potential energy in the instantaneous structure of the system. We find that these structural heterogeneities correlate with dynamical heterogeneities in the form of clusters of low molecular mobility.