What are the roles to optimize the elemental composition of an alloy/compound, for example there are some researchers who used the same alloy in different elemental ratios like, Mg3.2Sb1.5Bi0.49Te0.01, Mg3.3Sb0.5Bi1.298Te0.02, Mg3.3Sb0.5Bi1.498Te0.02 and Mg3.2Sb0.7Bi1.298Te0.02. What should be the proper/Scientific way to further optimize for the constituent elements.?