Alloying: What is it, why is it done and what is the equation of alloying?

Alloying is the process of mixing two different components to form a solid solution. It is done to tune the band gap to a desired energy. Band gap equation is Eg,AB = xEg,A + (1 − x)Eg,B − bx(1 − x), where x is the fraction of A in the alloy, and b is the bowing parameter.