title: Accurate evaluation of the angular-dependent direct correlation function of water.
abstract: The direct correlation function (DCF) plays a pivotal role in addressing the thermodynamic properties with non-mean-field statistical theories of liquid state. This work provides an accurate yet efficient calculation procedure for evaluating the angular-dependent DCF of bulk SPC∕E water. The DCF here represented in a discrete angles basis is computed with two typical steps: the first step involves solving the molecular Ornstein-Zernike equation with the input of total correlation function extracted from simulation; the resultant DCF is then polished in second step at small wavelength for all orientations in order to match correct thermodynamic properties. This function is also discussed in terms of its rotational invariant components. In particular, we show that the component c112(r) that accounts for dipolar symmetry reaches already its long-range asymptotic behavior at a short distance of 4 Å. With the knowledge of DCF, the angular-dependent bridge function of bulk water is thereafter computed and discussed in comparison with referenced hard-sphere bridge functions. We conclude that, even though such hard-sphere bridge functions may be relevant to improve the calculation of Helmholtz free energies in integral equations or density functional theory, they are doomed to fail at a structural level.
authors.affiliation: State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200238, China. szhao@ecust.edu.cn
authors.forename: Shuangliang
authors.initials: S
authors.lastname: Zhao
authors.forename: Honglai
authors.initials: H
authors.lastname: Liu
authors.forename: Rosa
authors.initials: R
authors.lastname: Ramirez
authors.forename: Daniel
authors.initials: D
authors.lastname: Borgis