MODEL FOR CORRELATED MOLECULAR ROTATION

We report studies of models designed to emphasize the thermodynamic consequences of coupled molecular rotation in condensed phases. The coupling arises from hard molecular cores of nonspherical shape, here represented by flat coplanar squares in a one-dimensional array. Various forms are considered for the orientation-independent part of the interaction, from none to harmonic to delta function (or lattice model) ; the first and third are shown to represent the high- and low-temperature limits of the second, treated classically. The lattice model gives rise to a particular sort of first-order phase transition, the significance of which is clarified by the temperature dependence of the properties of the harmonic model.