Regular solution theory revisited

The issue of whether a semiconductor alloy is really soluble is essential to the success of its design. Fortunately, reasonable models of solubility exist and can be applied to these materials. The stability of semiconductor alloys can be treated at least approximately with regular solution theory (see Chapter 4), which works well enough to give an idea of the general behavior of alloys including ternary and quaternary systems. 

Gibbs free energy, AG, with changes in composition  

When one configuration of a system has a distinctly lower free energy than another then that is the configuration the system chooses. In this section, we will consider an extension of the model in Chapter 4 to the calculation and minimization of this 

In conventional regular solution theory, the change of the bond energy for a simple binary AB solution upon mixing (as in Chapter 4) is given by 

The configurational entropy for a system with clustering described by the qj distribution probabilities above has been estimated for a zincblende semiconductor alloy to be a modified regular solution entropy, [6] 

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