derson [76, 77] for atomic fluids to chain-like fluids. It is a second-order perturbation
theory, in which the Helmholtz free energy is given as a sum of first- and second-order
contributions, as
^disp j^disp ^disp
(2.20)
NKT = NKT + NKT'
For chain-like molecules, the first and second term of the perturbation expansion have
the following form
/I '^>'>-'t' ________ ________ zr
Zl1 τ r' X ʌ z ∖ 4
(2.21)
= -2πpl1 ^^xixjmimj(-)σij,
i j
and
NKT
= —крЪт
± + Zhc + H ∑ xixjmimj⅛)¾
' i j
(2.22)
where Zhc is the compressibility factor of the hard-chain fluid, the parameters eŋ and
σij are obtained by conventional Berthelot-Lorentz mixing rules, m is the average
chain length of the mixture defined as
(2.23)
771 = ximiι
i
and ʃi and I<z are integrals given as
(2.24)
45