In theoretical chemistry, density functional theory (DFT) is a crucial topic. I would like to study DFT from scratch in order to learn about the condensed-phase environment. Could you suggest some free resources for me to use in my study?
Are you going to study on the theory or the application of the theory.
If the first one, you will need to read the classic paper about DFT, which you can easily get from google scholar.
If the second one, you can start from a tutorial of some DFT based softwares such as VASP (commercial), (non-commercial) QE, GPAW, etc... In these tutorials, there are often some theorical introductions you can learn the basic conception of DFT.