Thermodynamic perturbation theory for simple polar fluids, I
- 1 February 1972
- journal article
- research article
- Published by Taylor & Francis in Molecular Physics
- Vol. 23 (2), 393-406
- https://doi.org/10.1080/00268977200100381
Abstract
The application of thermodynamic perturbation theory to the computation of the properties of simple polar fluids is considered. The Helmholtz free energy of a fluid of molecules interacting via a Stockmayer potential v S is computed through fourth order in μ, where μ is the dipole moment. Numerical results are obtained on the basis of both the ‘exact’ Monte-Carlo computations for a Lennard-Jones system and the Verlet-Weis perturbation-theoretic computations for that system. The results obtained on the latter basis are then compared with results for a fluid of molecules interacting via a central-force potential v ES that is conformal with the Lennard-Jones 6–12 potential and equivalent to the Stockmayer potential through order μ4. To facilitate the comparison the v ES results are computed according to the Verlet-Weis method. The v ES results and the fourth-order (in μ) v S results constitute two different approximations to the thermodynamics of the Stockmayer potential; the compressibility factors as well as the free energies of the two approximations are compared. It is concluded that the thermodynamic contribution of the dipole term of v S is significant over the whole liquid region when μ2=εσ3, where ε and σ are the usual Lennard-Jones parameters. For this μ, the two approximations we consider give results in close agreement.Keywords
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