The correlations in a star molecule fluid. Integral equation theory and Monte Carlo study

The structure of a starlike molecule (SLM) fluid with four arms of differen t length is studied by applying the associative Percus-Yevick integral equa tion (IE) theory and canonical Monte Carlo (MC) simulations. In the IE stud y the SLM fluid is modelled by a fluid of hard spheres with four associativ e sites on each sphere while the MC has been performed for a freely-joined tangent hard sphere fluid. The total radial distribution functions have bee n calculated in both approaches for different volume fraction regimes and d ifferent arm lengths. It is shown that the associative IE theory predicts t he structure of SLM fluid best for relatively long arms and at high densiti es. Additionally, the dependence of the SLM centre-centre correlations on t he functionality and fluid particle density has been analysed using the MC results.