158 Perturbation Theories for Fluids and Solids
of the OZ equation for the fully interacting system, where c
0
(r) is the DCF of the
reference HS fluid. Note the resemblance of Equation 6.119 with the SCOZA closure
(4.26), but now the consistence is imposed through Equation 6.118 to every stage of
the switching on of the perturbation.
6.7 USING NON-HARD-SPHERE REFERENCE SYSTEM
Although in most cases the HS system is taken as the reference system, other choices
are possible and in some cases may be advantageous. Thus, Melnyk et al. (2007)
have proposed to use a short-ranged HCY fluid as the reference system, and the
difference between the actual and the reference potentials beyond the hard core as the
perturbation. They showed that this choice is adv