In recent years we have reported on density functional (DF) and Monte Carlo calculations on organic polymers, particularly bisphenol-A polycarbonate (BPA-PC). DF calculations provide essential information on the energy surfaces of the polymer and its reactants, and the results are used to derive the parameters of a simplified force field model. Monte Carlo calculations with this model have then provided new information about the polymerization and its driving force. We are extending these ideas to study liquid sulphur, often viewed as the simplest of all polymer systems. We describe DF calculations for the structures and cohesive energies of sulphur clusters and their reactions with each other. These provide essential input for Monte Carlo calculations now in progress.