Dynamics in a supercooled molecular liquid: Theory and simulations

We report extensive simulations of liquid supercooled states for a simple three-site molecular model, introduced by Lewis and Wahnstrom [Phys. Rev. E >50, 3865 (1994)] to mimic the behavior of ortho-terphenyl. The large system size and the long simulation length allow us to calculate very precisely (in a large q-vector range) self-correlation and collective correlation functions, providing a clean and simple reference model for theoretical descriptions of molecular liquids in supercooled states. The time and wave-vector dependence of the site-site correlation functions are compared (neglecting the molecular constraints) with detailed ideal mode-coupling theory predictions. Except for the wave-vector region where the dynamics are controlled by the center of mass (around 9 nm-1), the theoretical predictions compare very well with the simulation data