The A in SAFT: developing the contribution of association to the Helmholtz free energy within a Wertheim TPT1 treatment of generic Mie fluids
| Autor: | Amparo Galindo, Carlos Vega, Gary N. I. Clark, Thomas Lafitte, George Jackson, Andrew J. Haslam, Simon Dufal |
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| Přispěvatelé: | Qatar Shell Research and Technology Center QSTP LLC, Engineering & Physical Science Research Council (EPSRC), Pfizer Incorporated, Qatar Petroleum |
| Jazyk: | angličtina |
| Rok vydání: | 2015 |
| Předmět: |
integral equation theory
Association (object-oriented programming) Biophysics Thermodynamics Physics Atomic Molecular & Chemical symbols.namesake HYPERNETTED-CHAIN EQUATION Chain (algebraic topology) LENNARD-JONES FLUID HYDROGEN-BONDED FLUIDS PHASE-EQUILIBRIA CALCULATIONS STATISTICAL-MECHANICAL MODELS 0307 Theoretical and Computational Chemistry Statistical physics PERCUS-YEVICK APPROXIMATION Physical and Theoretical Chemistry Perturbation theory Representation (mathematics) Molecular Biology complex associating fluids Complex fluid perturbation theory 0306 Physical Chemistry (incl. Structural) Science & Technology Chemical Physics Basis (linear algebra) Chemistry Chemistry Physical Physics THERMODYNAMIC PERTURBATION-THEORY Statistical mechanics Condensed Matter Physics hydrogen bonding EQUATION-OF-STATE Helmholtz free energy Physical Sciences 0202 Atomic Molecular Nuclear Particle and Plasma Physics symbols DIRECTIONAL ATTRACTIVE FORCES statistical mechanics MONTE-CARLO SIMULATIONS |
| Popis: | An accurate representation of molecular association is a vital ingredient of advanced equations of state (EOSs), providing a description of thermodynamic properties of complex fluids where hydrogen bonding plays an important role. The combination of the first-order thermodynamic perturbation theory (TPT1) of Wertheim for associating systems with an accurate description of the structural and thermodynamic properties of the monomer fluid forms the basis of the statistical associating fluid theory (SAFT) family of EOSs. The contribution of association to the free energy in SAFT and related EOSs is very sensitive to the nature of intermolecular potential used to describe the monomers and, crucially, to the accuracy of the representation of the thermodynamic and structural properties. Here we develop an accurate description of the association contribution for use within the recently developed SAFT-VR Mie framework for chain molecules formed from segments interacting through a Mie potential [T. Lafitte, A. Apostolakou, C. Avendaño, A, Galindo, C. S. Adjiman, E. A. Müller, and G. Jackson, J. Chem. Phys. 139, 154504 (2013)]. As the Mie interaction represents a soft-core potential model, a method similar to that adopted for the Lennard-Jones potential [E. A. Müller and K. E. Gubbins, Ind. Eng. Chem. Res. 34, 3662 (1995)] is employed to describe the association contribution to the Helmholtz free energy. The radial distribution function (RDF) of the Mie fluid (which is required for the evaluation of the integral at the heart of the association term) is determined for a broad range of thermodynamic conditions (temperatures and densities) using the reference hyper-netted chain (RHNC) integral-equation theory. The numerical data for the association kernel of Mie fluids with different association geometries are then correlated for a range of thermodynamic states to obtain a general expression for the association contribution which can be applied for varying values of the Mie repulsive exponent. The resulting SAFT-VR Mie EOS allows for a much improved description of the vapour-liquid equilibria and single-phase properties of associating fluids such as water, methanol, ammonia, hydrogen sulphide, and their mixtures. A comparison is also made between the theoretical predictions of the degree of association for water and the extent of hydrogen bonding obtained from molecular simulations of the SPC/E and TIP4P/2005 atomistic models. |
| Databáze: | OpenAIRE |
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