An integral equation study of liquid acetonitrile

Abstract

The site-site Ornstein-Zernike (SSOZ) equation coupled with the hypernetted chain (HNC) closure is solved numerically using Gillan's method, for a six site potential model for acetonitrile. The site-site radial distribution functions are in good agreement with available molecular dynamics data. It was found that the dipole-dipole interactions play an important role in determining the short range local structure in liquid acetonitrile, with two types of orientation between neighbouring molecules being preferred. These are firstly, an antiparallel, side by side arrangement and secondly, a parallel but end to end orientation. As predicted in previous work, the dipole-dipole interactions were found to have virtually no effect on the calculated scattering function. We describe a procedure for utilizing the symmetries within the Jacobian matrix in the numerical solution. This procedure is general for molecules of arbitrary symmetry and was found to reduce the computation time required to obtain the numerical solution for acetonitrile by an order of magnitude.