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| Titel: |
The 'convex peg' model: the long range approximation |
| Auteur: |
WILLIAMSON, DAVE C. |
| Verschenen in: |
Molecular physics |
| Paginering: | Jaargang 95 (1998) nr. 2 pagina's 319-329 |
| Jaar: |
1998-10-10 |
| Inhoud: |
A first-order Barker-Henderson-type perturbation theory is presented for the 'convex peg' model. The long range approximation of Ponce and Renon for the spherical square-well fluid is used in conjunction with Parsons' decoupling approximation. With these approximations the theory should be applicable for prolate hard cores with aspect ratios greater than 3:1:1 and oblate hard cores of aspect ratio greater than 1/8:1:1. The theoretical predictions are tested against the available simulation data in the vapour—liquid region of the phase diagram. Away from the critical point, the theory provides an excellent description of the vapour-liquid envelope for the fluid with a prolate uniaxial core 3:1:1. As expected, for the 1/3:1:1 model the results are in poor agreement with the simulation data. The theory is extended to include the nematic phase, and a vapour-liquid-nematic triple point is predicted below which the nematic phase coexists with the vapour phase. This has been seen for the same model in a van der Waals type theory; however, to date there are no simulation data to confirm this. The 'convex peg' with 3:1:1 core is used to model the I—N phase transition of p-azoxyanisole, and gives reasonable results for some thermodynamic properties. Although the use of a biaxial core should improve a comparison between theory and experiment for some of the other properties, it would appear that the 'convex peg' lacks certain features for necessary in a model of a real nematogen. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 28 van 33 gevonden artikelen
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