ABSTRACT
However, as an approximation, the LDA cannot be successful for all systems although the exact DFf should be capable of obtaining groundstate properties. Strongly correlated materials are examples where the deficiency of the LDA is seen most clearly. Such systems usually contain transition-metal or rare-earth metal ions with a partially filled d-(or f-) shell. When applying a one-electron method with an orbital-independent potential, like in the LDA, to transition-metal compounds, one has as a result a partially filled d-band with metallic type electronic structure and itinerant d-electrons. This is definitely a wrong answer for the late-transition-metal oxides and rare-earth metal compounds where d-(f-)electrons are well localized and there is a sizable energy separation between occupied and unoccupied subbands (the lower Hubbard band and upper Hubbard band in a model Hamiltonian approach).
