Doping, composite, and alloying are three different techniques that are used to modify the properties of materials. Here are the definitions of each:
Doping: Doping is the process of introducing impurities into a material to modify its electrical or optical properties. This is commonly used in semiconductors, where small amounts of impurities are added to control the electrical conductivity.
Composite: A composite material is a combination of two or more materials that have different properties. These materials are combined in a way that enhances the properties of the individual materials, resulting in a material that is stronger, lighter, or more durable than the original materials.
Alloying: Alloying is the process of combining two or more metals to create a new material with enhanced properties. This is commonly used in metallurgy to create stronger, more durable metals.
The boundary between these techniques is not always clear-cut, as there can be some overlap between them. For example, a composite material could be made by combining two different alloys. However, the main difference is that doping is typically used to modify the properties of a single material, while composites and alloys involve the combination of multiple materials.
Regarding your question about alloying in DFT, yes, alloying is possible in DFT. In fact, DFT calculations are commonly used to study the properties of alloys and predict their behavior under different conditions.
As for your idea of alloying FeAs and CdTe for computational purposes, it is feasible in principle, but it would depend on the specific properties you are interested in studying. You would need to perform DFT calculations to determine the stability and properties of the alloy and compare them to those of the individual compounds.