Reconsidering power functional theory.

The original derivation of power functional theory [M. Schmidt and J. M. Brader, J. Chem. Phys. 138, 214101 (2013)] is reworked in some detail with a view to clarifying and simplifying the logic and making explicit the various functional dependencies. We note various issues with the original development and suggest a modification that allows us to avoid them. In the process, we also suggest an alternative interpretation of our results, which bears surprising similarities to classical density functional theory.