The bridge functions are infinite series of irreducible diagrams :
where is the density of the fluid.
Universality of the Bridge functional
For Rosenfeld's principle of the universality of the bridge functional see Ref. 2.
- Jean-Marc Bomont and Jean-Louis Bretonnet "Approximative “one particle” bridge function B(1)(r) for the theory of simple fluids", Journal of Chemical Physics 126 214504 (2007)
- Yaakov Rosenfeld "Free energy model for inhomogeneous fluid mixtures: Yukawa-charged hard spheres, general interactions, and plasmas", Journal of Chemical Physics 98 pp. 8126-8148 (1993)