Light-Scattering by Longitudinal phonons in Supercooled Molecular Liquids II: Microscopic Derivation of the Phenomenological Equations

The constitutive equations for the orientational dynamics of a liquid formed of linear molecules are derived microscopically. The resulting generalised Langevin equations coincide with the phenomenological approach of Dreyfus et al. Formally exact expressions are given for the phenomenological coefficients and various constraints are shown to be consequences of this microscopic approach.