  We develop the first comprehensive approach to model associating fluids with
small bond angles using Wertheim's perturbation theory. We show theoretically
and through monte carlo simulations that as bond angle is varied various modes
of association become dominant. The new theory is shown to be in excellent
agreement with monte carlo simulation for the prediction of the internal
energy, pressure and fractions in rings, chains, double bonded over the full
range of bond angles.
