Ab initio DFT – the seamless connection between WFT and DFT

Abstract

Orbital-dependent exchange-correlation functionals and potentials play an increasingly important role in Density Functional Theory (DFT). Methods which use explicit orbital-dependent functionals can be viewed as a natural extension to the standard Kohn–Sham (KS) procedure in DFT, that traditionally have used functionals with explicit density-dependence but only implicit orbital-dependence. Ab initio DFT, invented at the Quantum Theory Project, is the method which could define rigorous orbital-dependent exchange-correlation functionals and potentials in the context of KS DFT theory. The local and multiplicative exchange-correlation potentials are derived from a general theoretical framework based on the density condition in KS theory and from coupled-cluster theory and many-body perturbation theory. Ab initio DFT guarantees to converge to the right answer in the correlation and basis set limit, just as does ab initio Wave Function Theory (WFT) and solves in a rigorous way most of the shortcomings of standard density-dependent KS DFT. It is also the route toward understanding the relationships between traditional ab initio WFT and DFT.

The Optimized Effective Potential ‘journey’ on the borderline of WFT and DFT was inspired and possible only because of the Quantum Theory Project where we stayed as postdocs in 1999–2001. It seems to us then we were in the right place and at the right time, and certainly with the right people. The QTP scientific melting pot and Sanibel's meetings gave us an excellent possibility to work together, learn and hopefully solve many important scientific problems.

Keywords:

• optimized effective potential method
• electron correlation
• density functional theory
• ab initio DFT

Acknowledgements

This work was supported by the Polish Committee for Scientific Research MNiSW under Grant no. N N204 560839. S. Hirata was supported by the U.S. National Science Foundation (CHE-0844448), the U.S. Department of Energy (DE-FG02-04ER15621), and the Donors of the American Chemical Society Petroleum Research Fund (48440-AC6). S. Hirata is a Camille Dreyfus Teacher-Scholar. We appreciate many informative discussions with Dr. Ajith Perera and Dr. Igor Schweigert. And we would like to thank Rod Bartlett for his ideas, stimulation, ‘black board discussions’, and for giving us opportunity to work together in Quantum Theory Project.