UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2024-11-22 1:30
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Conference: Bucharest University Faculty of Physics 2010 Meeting


Section: Theoretical Physics and Applied Mathematics


Title:
Theoretical Binodal and spinodal curves for three-component solution


Authors:
Radu Paul Lungu


Affiliation:
University of Bucharest, Department of Physics


E-mail
RaduPLungu@yahoo.com


Keywords:
Ising models, phase transitions


Abstract:
A tree-component solution is described as a spin system, using a generalized Wheeler-Widom model on a 3-12 lattice and with three-body interactions between neighboring spins; then, this spin system is put into a direct correspondence with a simple Ising model on a honeycomb lattice. The mole fractions of the three components can be expressed in terms of the magnetization and the spin-spin correlation function of the associated Ising model. In order to use the theoretical results for comparison with the experimental data the simple Ising model is considered in the mean field approximation. At constant temperature, the molecular system can exhibit a phase transition, and the analytic expressions for binodal (the curve that describes the phase equilibrium), together with the spinodal (the limit of the meta-stable states) are obtained. In order to correlate the theoretical results with the experimental data, the following method for local fitting is used: a) from the set of the experimental points of the binodal is obtained the interpolated experimental binodal; b) in a set of points from the interpolated experimental spinodal are applied the conditions for local fitting between the interpolated experimental binodal and the theoretical binodal; c) from these conditions it follows the parameters of the theoretical model corresponding to each fitting point; d) using the values of these parameters, the local spinodals are obtained; e) the spinodal points corresponds to the intersections of the local theoretical left and right spinodals with the local theoretical tie-line; f) the resulting theoretical spinodal is the interpolated curve of the local spinodal point set. The results are in agreement with experimental data for spinodal curves for water-chloroform-acetic acid solution.