Solution models quasi-regular

The entropy of mixing of many real solutions will deviate considerably from the ideal entropy of mixing. However, accurate data are available only in a few cases. The simplest model to account for a non-ideal entropy of mixing is the quasi-regular model, where the excess Gibbs energy of mixing is expressed as... 

If the second term in the configurational entropy of mixing, eq. (9.42), is zero, the quasi-chemical model reduces to the regular solution approximation. Here, Aab is given by (eq. (9.21). If in addition yAB =0the ideal solution model results. 

T entropy term in the quasi-regular solution model... 

Essentially, we are looking at the solubility of metals in other metals - i.e. monophase metal alloys. The most commonly used solution models are the models with similar atomic volumes, which give us the perfect solution, the infinitely-dilute solution and the strictly-regular solution. Thus, we will then look at Guggenheim s quasi-chemical model, which includes the notion of short-distance order. 

In order to evaluate the functions g(5) and E s), we need to know the distribution of the atoms on the lattice for the given value of s. Two models have been developed the Gorsky, Bragg and Williams model and the quasi-chemical model. The hypotheses upon which these models are based are similar, respectively, to those used for the model of a strictly-regular solution (see section 2.3.3) and those used for Fowler and Guggenheim s quasi-chemical solution model (see section 2.3.5). 

According to the basic principles of the regularization method, we have to find a quasi-solution of the inverse problem as the model ma that minimizes the parametric functional... 

Figure 3.2. Comparison of the excess Gibbs energies of a strictly-regular solution and the quasi-chemical model (reproducedfrom [DES10], p.62 - see Bibliography)...

Saxena (1973). A general account of the mixing properties of crystalline solutions, with detailed discussions of the van Laar, regular (one coefficient, symmetric), "sub-regular" (two-coefficient, asymmetric) and quasi-chemical models. Margules and other equations for i presented for binary... 

The thermodynamic data of polymer solutions were first derived from the approach of regular solutions of small molecules by Flory [29] and by Huggins [30]. In the original quasi-lattice model of Flory, the interaction parameter, x, was representative of the enthalpic difference of polymer/polymer, sol-vent/solvent and polymer/solvent contacts. Progressively % lost this simple signification and represented the shift with an ideal behavior (including entropic effects) but nevertheless the model was established for... 

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