The homologous series of n-alkanes are represented here as homonuclear chains of tangent Mie spherical CG segments. The development of CG models for long n-alkanes such as n-decane (n-C10H22) and n-eicosane (n-C20H42) has already been successfully demonstrated using the SAFT-γ Mie formalism [118]. The n-decane molecule was represented by chains of three and n-eicosane chains of six fully flexible tangentially bonded Mie segments. A certain degree of parameter degeneracy in terms of overall performance is expected as a consequence of the conformal nature of the EOS description [132]. In our current work, we use an alternative CG mapping for n-alkanes developed in reference [122], where each segment was taken to represent three alkyl carbon backbone atoms and their corresponding hydrogen atoms. By applying this mapping, n-alkanes chains containing multiples of three carbon units can be represented directly: n-C6H14, n-C9H20, n-C12H26, n-C15H32, n-C18H38, etc. A good description of the thermodynamic properties of these alkanes is found to be provided with CG alkyl beads characterised by the Mie (15–6) potential. For convenience, the exponent pair (15–6) is also used to represent the interactions between the CG beads of the intervening alkanes considered here; the number of segments m is taken to be the nearest integer of the division of the carbon number C by three. The size σ and energy ∊ parameters are then estimated from the experimental saturated-liquid density and vapour pressure of the individual alkanes following the usual SAFT-γ Mie procedure. The chosen mapping is by no means unique, as one can postulate parameter sets that fulfil other requisites, such as being “universal” across the entire homologous series [119] or correlated to the critical properties [125].
