MONTE CARLO STUDY OF HARD SPHEROCYLINDERS. III. THE ANGULAR CORRELATION FUNCTIONS I. NEZBEDA Institute of Chemical Process Fundam™ Czechosl. Acad. Sci., Pra#ue*) Monte Carlo simulation method has been used to study angular correlations in the fluid of hard spherocylinders of the length/breadth ratio equal to 1"4, 1'6, and 2"0, respectively. The correlation functions have been evaluated both by means of the spherical harmonic expansion and directly (at specific orientations) which enabled us to examine convergence of the former approach. The possibility of the 'bottleneck effect' has been investigated as well using two different simula- tion schemes. 1. INTRODUCTION Computer simulation studies have contributed considerably to progress in the field of liquid theories (for a review see e.g. [1]). They provide not only astringent test of analytic theories, but also an insight into profitable directions for further theoretical development. In some cases, like e.g. for the hard convex bodies (hcb), we have to resort to simulations as to the only source of our understanding of ordering in the system. In two recent papers [2, 3] of our series of Monte Carlo (MC) simulations of hard spherocylinders we reported resultS on the average surface-to-surface correlation function, g~. It enabled us to evaluate the MC equation of state of spherocylinders and verify a theoretical one [4]. Though the knowledge of the g~ pushed theoretical studies of nonpolar molecular fluids forward [5] its further usefulness remains rather limited. Besides the fact that it does not provide any information on the structure ofthe system it may be exploited in perturbation schemes only for systems whose particles interact via the Kihara-core potential. Complete information on both the thermodynamic and structural properties can be obtained from the full two-particle correlation function g(RI 87 01, 02). However, unlike other nonspherical molecule systems (like e.g. hard dumbells), very little is known about g of the hcb fluid [6]. Therefore, and in order to complete out MC simulations in the hard linear molecule fluid, the system of spherocylinders of the lcngth/breadth ratio equal to 1.4, 1.6, and 2., respectively, has been studied. Besides aiming at the usual MC simulation outcomes, i.e. to find the compressibility factor and the coefficients in the expansion of g in the spherical harmonics, there have been two other aims of out investigations: (i) To study a possibility of the 'bottleneck effect' which may occur when an impro~ per simulation scheme is used [7]; *) Suchdol 2, 165 02 Praha 6, Czechoslovakia. Czech. J. Phys. B 30 [1980] 601