Effective intermolecular potentials in theoretical thermodynamics of pure substances and solutions

Thermodynamic Properties of Ar, Kr and Xe from a Monte Carlo- Based Perturbation Theory with an Effective Two-Body Lennard-Jones Potential

“…On the opposite side, one of the main strengths of the present theory is its generality because, as already pointed out, it can be applied to any fluid whose two-body interactions are satisfactorily described by the Lennard-Jones potential, in contrast with most other approximations proposed in the literature that are system dependent, as is the case of those reported in Refs. [ 4,5,8,10). Another remarkable fact is that, although it was not expected in advance for a theory that does not account specifically for critical phenomena, our theory provides fairly good predictions for the coexistence curves.…”

“…A different way of taking into account the effect of the three-body interactions in the thermodynamic properties consists in using effective two-body potentials that include the three-body contribution. To this end, del Rio et al (7)(8)(9)(10) introduced a family of effective potentials, denoted as approximate non conformal (ANC) potentials, involving a number of parameters that are determined from the condition that certain thermodynamic properties, such as the second and third virial coefficients and the pressure at some selected states, determined from the effective potential, for example by computer simulation, fit the corresponding experimental data. The effective potential obtained in this way is state-dependent.…”

Third virial coefficient of nonpolar gases from accurate binary potentials and ternary forces

“…As a first approximation, ANC potentials are used to represent the two-body interactions because they reproduce very accurately the experimental data for the second virial coefficient B exp (T ) of the substances studied [38][39][40][41]. As the ANC family includes potential profiles with different degrees of softness, a particular ANC interaction is determined by three molecular parameters: the depth (ε) and position (δ) of the potential well, and the softness (s) of the potential profile [42,43]; its functional form corresponds to a modified Kihara potential…”

“…Two-body parameters were taken from [38][39][40][41], with the exception of the acoustic set of argon [48] (second entry for Ar). The ATM coefficient ν was taken from the indicated references, or approximated [43] when no reference is given. reduced ANC potentials share the same minimum at (1, −1), but differ in the width of the potential well.…”

“…reduced ANC potentials share the same minimum at (1, −1), but differ in the width of the potential well. Large values of s result in potentials with a well wider than the reference (soft potentials), and values of s close to zero result in sharp potential wells (hard potentials) [43].…”