Monte Carlo simulations of symmetric and asymmetric angular model liquids

Monte Carlo simulations of fluids made of nonpolar angular alpha beta gamma molecules in the NVT ensemble have been performed. They provide quantitati ve information on the influence of alpha beta and beta gamma distances (L-a lpha beta and L-beta gamma), temperature and density on the pressure, inter nal energy, and structural functions of these fluids. Three different model s have been considered. The first one is a symmetric angular model of propa ne with L-alpha beta = L-beta gamma = 0.4123 in reduced units. A detailed i nvestigation of the thermodynamic and structural properties of this alkane is presented here. The results of the present study are in agreement with t hose obtained by previous molecular dynamics simulation and with experiment al data. The second model consists of nonsymmetrical molecules in which L-a lpha beta = 0.4123 and L-beta gamma = 0.6 (reduced units). The third model is a symmetrical one with L-alpha beta = L-beta gamma = 0.6, a larger dista nce than for propane. Differences in the critical properties for each model are estimated and differences on the variation of the critical temperature with the molecular shape are discussed. Some preliminary comparisons among simulations and x-ray diffraction experiments in liquid propane are also p resented. (C) 2001 American Institute of Physics.