Correlations in Hard- and Soft-Core Generic Polymer Models*

Generic polymer models capturing the chain connectivity and the non-bonded excluded-volume interactions between polymer segments can be classified into hard- and soft-core models depending on their non-bonded pair potential. Here we compared the correlation effects on the structural and thermodynamic properties of the hard- and soft-core models given by the polymer reference interaction site model (PRISM) theory. The behavior of soft-core models at large invariant degree of polymerization depends on how it is varied, i.e., whether by changing the chain length N at fixed segment number density ρ (thus the excluded-volume interaction parameter ε is fixed) or by changing ρ at fixed N (thus ε is also varied as being inversely proportional to ρ). We also proposed an efficient numerical approach, which enables us to accurately solve the PRISM theory for N as large as 10⁶.