Nematic ordering in the lattice model with attractive isotropic interaction

The athermal lattice model in which elongated rigid molecules are simulated by rows of consecutive sites is generalized so as to include an attractive segment–segment interaction energy—ε. Thus a distinction is made between a liquidlike phase and a supercritical gas phase. The model is solved in the Bethe–di Marzio and in the quasichemical approximation. The presence of such an attractive interaction leads to a reasonable p,T diagram of state provided r=4 or 5 in three or six dimensions. For longer rods, only the phase transition from the supercritical gas with very large volume changes is obtained already for r?6.