Bridge function of the repulsive Weeks–Chandler–Andersen (WCA) fluid

The bridge function of a simple liquid is calculated for the repulsive part of the Weeks–Chandler–Andersen (WCA) separation of the Lennard–Jones potential. We employ explicit molecular dynamics simulations of the potential of mean force between constrained dimers in order to extract bridge data near zero separation and illustrate the difference to full Lennard–Jones results. We compare direct, reciprocal space and iterative, real space inversions of the Ornstein–Zernike equation. Bridge functions for various thermodynamic states are analyzed as to their parametric dependence on the renormalized indirect correlation function, which has consequences for the analytic representation of the free energy functional.