Liquid lattice model ideal solution

Temkin was the first to derive the ideal solution model for an ionic solution consisting of more than one sub-lattice [13]. An ionic solution, molten or solid, is considered as completely ionized and to consist of charged atoms anions and cations. These anions and cations are distributed on separate sub-lattices. There are strong Coulombic interactions between the ions, and in the solid state the positively charged cations are surrounded by negatively charged anions and vice versa. In the Temkin model, the local chemical order present in the solid state is assumed to be present also in the molten state, and an ionic liquid is considered using a quasi-lattice approach. If the different anions and the different cations have similar physical properties, it is assumed that the cations mix randomly at the cation sub-lattice and the anions randomly at the anion sub-lattice. 

The basic lattice models of liquid state are the quasi lattice model, the cell model, the free volume model, the hole model, the cluster model, the tunnel model, etc. The use of models in thermodynamic treatment of solutions to express deviation from ideality, such as excess thermodynamic functions, offers the advantage of compensating for the approximation involved in models, affecting to an equal extent the functions of the mixture and the single components. 

Figure 16.1 The vapor pressure p/j ofmolecules over a liquid solution having composition Xn, according to the lattice model. Increasing the concentration Xb of B in the liquid increases the vapor pressure of /i. x = 0 represents an ideal solution. B has more escaping tendency when x > arid less when x < 0, for a given Xb-...

Alternative ways of accounting for precocious deviations from ideality in solid-liquid distributions involve consideration of configurational entropy effects in the solid solution process. Two of these are the two ideal sites model (Matsui and Banno, 1962 Grover and Orville, 1969) and the local lattice distortion model (liyama, 1974). 

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