Perturbation theory Helmholtz free energy

Tarazona and Navascues have proposed a perturbation theory based upon the division of the pair potential given in Eq. (3.5.1). In addition, they make a further division of the reference potential into attractive and repulsive contributions in the manner of the WCA theory. The resulting perturbation theory for the interfacial properties of the reference system is constructed through adaptation of a method developed by Toxvaerd in his extension of the BH perturbation theory to the vapor-liquid interface. The Tarazona-Navascues theory generates results for the Helmholtz free energy and surface tension in addition to the density profile. Chacon et al. have shown how the perturbation theories based upon Eq. (3.5.1) may be developed by a series of approximations within the context of a general density-functional treatment. 

A well-rounded EoS should be able to accurately predict thermodynamic properties over a wide range of temperatures and pressure in each of the snbcritical, critical and supercritical regions. In this work, PC-SAFT is used for the prediction of thermodynamic properties. PC-SAFT is based on perturbation theory and is formnlated in terms of the residnal Helmholtz free energy, A. In the perturbation theory, A is modeled as the sirm of contributions from different intermolecular interactions over a reference fluid. In this respect. Gross and Sadowski [10] proposed the following expression which is an improvement over the original SAFT [11] ... 

In thermodynamic perturbation theory the properties of the real system, in which the pair potential is u° g, are expanded about the values for a reference system, in which the pair potential is ug3. Here we take the reference potential to be the (n,6) potential, so that the anisotropic parts of the potential in Eq. (1) are the perturbation. Expanding the Helmholtz free energy A in powers of the perturbing potential about the value Aq for the reference system gives... 

EoS based on perturbation theory and computer simulation results validity of the Barker-Henderson theory Derivation of the BGY, PY, and HNC integral equations in 2D Fourth virial coefficient Fifth virial coefficient Quantum corrections to the third and fourth virial coefficients quantum corrections to the Helmholtz free energy Results at very high densities EoS based on computer simulation results and on the five first virial coefficients No influence of number of particles for states far from the phase transitions values of RDF... 

The statistical-associated fluid theory (SAFT) of Chapman et al. [25, 26] is based on the perturbation theory of Wertheim [27]. The model molecule is a chain of hard spheres that is perturbed with a dispersion attractive potential and association potential. The residual Helmholtz energy of the fluid is given by the sum of the Helmholtz energies of the initially free hard spheres bonding the hard spheres to form a chain the dispersion attractive potential and the association potential,... 

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