Semischematic model for the center-of-mass dynamics in supercooled molecular liquids

We introduce a semischematic mode-coupling model to describe the slow dynamics in molecular liquids, retaining explicitly only the description of the center-of-mass degrees of freedom. Angular degrees of freedom are condensed in a q-vector independent coupling parameter. We compare the time and q dependence of the density fluctuation correlators with numerical data from a 250-ns-long molecular dynamics simulation. Notwithstanding the choice of a network-forming liquid as a model for comparing theory and simulation, the model describes the main static and dynamic features of the relaxation in a broad q-vector range. [S1063-651X(98)03201-2].