In DFT the exchange-correlation function is critical for the correct description of the system. I have a question about the applications and shortcoming of some functionals. LDA delocalizes electrons so are good for conductors. And pure HF localizes electrons so it's good for molecules/atoms.
So, is it safe to say that if one doesn't include correlation and only uses HF exchange energy that crystals, or any material with long range ordering, couldn't be properly described?
And the same around, if one only uses correlation, conducting crystals are properly described but no molecules/atoms could be studied correctly?
I want to understand the applications and limitations of both extremes and I am having a hard time finding that kind of analysis online.