Perspective: Kohn Sham density functional theory descending a staircase.
This article presents a perspective on Kohn Sham density functional theory (KS DFT) for electronic structure calculations in chemical physics. This theory is in widespread use for applications to both molecules and solids. We pay special attention to several aspects where there are both concerns and progress toward solutions. These include: 1. The treatment of open shell and inherently multiconfigurational systems (the latter are often called multireference systems and are variously classified as having strong correlation, near degeneracy correlation, or high static correlation; KS DFT must treat these systems with broken symmetry determinants) 2. The treatment of noncovalent interactions. 3. The choice between developing new functionals by parametrization, by theoretical constraints, or by a combination. 4. The ingredients of the exchange correlation functionals used by KS DFT, including spin densities, the magnitudes of their gradients, spin specific kinetic energy densities, nonlocal exchange (Hartree Fock exchange) nonlocal correlation, and subshell dependent corrections (DFT+U) 5. The quest for a universal functional, where we summarize some of the success of the latest Minnesota functionals, namely MN15 L and MN15, which were obtained by optimization against diverse databases. 6. Time dependent density functional theory, which is an extension of DFT to treat time dependent problems and excited states. The review is a snapshot of a rapidly moving field, and like Marcel Duchamp we hope to convey progress in a stimulating way.
The Journal of chemical physics