Quantum theory for chemical applications : from basic concepts to advanced topics Quantum Theory for Chemical Applications (QTCA) Quantum theory or more specifically quantum mechanics is endlessly fascinating curious & strange and often considered to be difficult to learn. It is true that quantum mechanics is a mathematical theory. Its scope its predictions the wisdom we gain from its results all these become fully clear only in the context of the relevant equations and calculations. But the study of quantum mechanics is definitely worth the effort and as I like to tell my students it is not rocket science