A density-functional theory for polymer liquids based on the interaction site model

The site-density integral equation (SDIE) for polymer liquids under an arbitrary external field was derived by the density-functional theory (DFT). The ideal chain gas was employed in order to make the DFT computationally tractable. Thus, many-body effects were considered through an effective external field acting on the ideal chain gas. The effectivie external field was described by the site-density expansion of the excess intrinsic chemical potential from the ideal chain gas up to the first order.