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Based on the statistical theory for chemical association,equations of state for hard-spherechain fluids(HSCFs)and square-well chain fluids(SWCFs)can be derived through the n-particlecavity correlation function(CCF)of the corresponding reference system,where n is the chain lengthor the number of segments of a chain molecule.The reference system is a fluid composed of only cor-responding monomers.In this work,the n-particle CCF is approximated by a product of effectivetwo-particle CCFs which accounts for correlations in nearest-neighbour and next-to-nearest-neighboursegment pairs.The CCFs for SWCFs may be expressed by a product of the corresponding functionfor HSCFs and a perturbation term originated from the square-well attractive potential.All these ef-fective two-particle CCFs and perturbation terms are density dependent.The dependence is determinedmainly by using computer-simulation results.The obtained equations can excellently describecompressibility factors and second Virial coefficients for HSCFs
Based on the statistical theory for chemical association, equations of state for hard-spherechain fluids (HSCFs) and square-well chain fluids (SWCFs) can be derived through the n-particlecavity correlation function (CCF) of the corresponding reference system, where n is the chain lengthor the number of segments of a chain molecule. The reference system is a fluid composed of only cor-responding monomers. In this work, the n-particle CCF is approximated by a product of effective two-particle CCFs which accounts for correlations in nearest-neighbor and next-to-nearest-neighboursegment pairs. the CCFs for SWCFs may be expressed by a product of the corresponding function for HSCFs and a perturbation term originated from the square-well attractive potential. All these ef-fective two-particle CCFs and perturbation terms are density dependent. The dependence is determinedmainly by using computer-simulation results. The resulting equations can excellently describecompressibility factors and second Virial coeff icients for HSCFs