Extraction of atom–atom bridge and direct correlation functions from molecular simulations: A test for ambient water

We compute partial structure factors for SPC/E water under ambient conditions, using radial distribution functions derived from simulations and employing finite-size corrections. We calculate atom–atom direct correlation functions by an inverse solution to reference interaction site model integral equations with account of long-range asymptotics of the functions as additional constraints. We split the short- and long-range contributions to the direct functions in the Ewald type manner. Finally we reconstruct atom–atom bridge functions. The obtained direct correlation functions are compared with the data obtained by the hypernetted chain approximation.