perturbation from the reference hard-chain fluid.
2.2.1 Chain term
From eqn. 2.1, the Helmholtz free energy of a mixture of hard-chain fluids is given
by
y∣⅛c _ I дЬз ∣ chain
(2.2)
(2.3)
The ideal free energy of the segments is given by
j∖id ' __v
= 22 mixi(lnpi -1) +C,
where the term ‘C’ includes the term involving the De Broglie wavelength. For re-
pulsive interactions, instead of using a purely repulsive hard sphere potential, softly-
repulsive potential suggested by Chen and Kreglewski [65] is used.
r <(σi- si)
^repulsion_ <
3ei {σi - sɪ) ≤ r < σi ,
(2.4)
r ≥ σi
where e is the depth of the potential well that quantifies the square-well attractive
interactions between the segments of the chains (as will be discussed in the dispersion
term), and si = 0.12σ. Following Barker and Henderson perturbation theory [77], this
soft repulsion between spheres can be described using a purely repulsive hard-sphere
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