The name is absent

3.2 Chandler, McCoy and Singer

Chandler, McCoy and Singer [98, 99] developed a DFT for polyatomic fluids within
the framework of interaction site model (ISM) [37]. In ISM, molecules are modeled
as chains of freely jointed spheres which interact with spherically symmetric site-site
potentials. These interacting sites coincide with the centers of their respective seg-
ments [103]. The free energy for such a system can be expressed as a functional
of the site densities, p_t'(r). A variational principle still exists which states that the
free energy has a global minimum for the equilibrium site densities. This free energy
functional has two contributions, an ideal part and a non-ideal∕excess part. The ideal
free energy takes only intramolecular interactions into consideration. This choice for
the ideal part of the free energy is not obvious and other choices are possible. For ex-
ample, McMullen and Freed [104] introduced a density functional formalism in which
they assumed no bonding constraints to define their ideal free energy. This ideal free
energy was, however, still different to that for a simple monomer fluid due to the
fact that the monomers retained their polymer labels. Moreover, calculation of the
CMS ideal free energy functional require a single chain simulation. The excess free
energy includes all the intermolecular interactions. This excess contribution is calcu-
lated from the site-site correlation function of the corresponding uniform fluid, which
is estimated by solving the Reference Interaction Site Model (RISM) equations [37]
or their extension to polymers (Polymer Reference Interaction Site Model (PRISM)
theory [105] ). This lead to inconsistencies in the theory due to approximations made

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