Chain fluids: contrasts of theoretical and simulation approaches, and comparison with experimental alkane properties

In this work, we undertake a fundamental comparison of analogous lattice and continuum integral equation theories, with both held accountable to the results from Monte Carlo simulation and real experimental data on short chain molecules. Each integral equation method is applied to determine the system's microscopic intermolecular site-site distributions and the corresponding bulk thermodynamic properties. These properties and those from the MC simulations are then fitted to corresponding data on n-alkanes. Thus, in side-by-side comparisons we cover a number of fundamental contrasts: theory versus simulation, lattice-based theory versus continuum-based theory, and thermodynamic properties of model chain molecules versus the actual experimental properties of hydrocarbons. The observed behavior of the modeling methods is compared in terms of both the experimentally accessible physical properties (e.g., PVT and coexistence properties) and the more fundamental underlying quantities, such as free energies and model internal energies. We also discuss the various options for model parametrization and subsequent impact on the predicted physical properties. The results from this work are used (alone, with no additional fitting) in the article which follows, wherein we predict the experimental properties of alkane mixtures.