theory or simulation

Theoretical activities attempt to fit mathematical frameworks over observed phenomena so that we have a rigorous way to describe them. In QM simulations for materials, we already have an agreed-upon and verified mathematical framework and not trying to describe anything – instead, that system is used to try and predict properties, behaviors, etc.

People may tend to have the opposite interpretation because “theory” may translate to simply “not empirical experimentation.” Computational activities fit within that definition, it’s just that the definition itself is not accurate to what theoretical activities actually are.