Mode coupling theory for molecular liquids: what can we learn from a system of hard ellipsoids?

Molecular fluids show rich and complicated dynamics close to the glass tran sition. Some of these observations are related to the fact that translation al and orientational degrees of freedom couple in non-trivial ways. A model system which can serve as a paradigm to understand these couplings is a sy stem of hard ellipsoids of revolution. To test this we compare at the ideal glass transition the static molecular correlators of a linear A-B Lennard- Jones molecule obtained from a molecular dynamics simulation with a selecte d fluid of hard ellipsoids for which the static correlators have been obtai ned using Percus-Yevick theory. We also demonstrate that the critical non-e rgodicity parameters obtained from molecular mode coupling theory for both systems show a remarkable similarity at the glass transition, provided the aspect ratio is chosen properly. Therefore we conclude that a system of har d ellipsoids can indeed be used to understand part of the essential behavio ur of such a simple molecular system like the A-B Lennard-Jones molecules i n the vicinity of the ideal glass transition.