A simple Semi-Explicit Density Functional Approach for Electron Systems

摘要

One of the main reasons of the great impact of density-functional theory in the current research in physics and chemistry is the possibility of studying microscopically the structure of complex systems for which other quantum mechanical methods are not applicable. Most of the applications of DFT are performed via the Kohn-Sham equations, which appear when the energy functional depends on the density via a set of electron orbitals (implicit density functional), as opposed to the first functionals used in this theory which depend only on the density itself, like the Thomas-Fermi and Thomas-Fermi-Dirac (explicit density functionals). For the challenge of the study of very complex systems, where the Kohn-Sham equations might be difficult to apply, these explicit functionals could be the only alternative for an ab-initio calculation, because of their extreme simplicity. However, there are different failures in the models derived by them, such as the no-binding feature (Teller's theorem), the no possibility of describing negative ions, a loss of precision in the calculation of average properties and the difficulties found for the relativistic extensions.