Chapter 3
Multi-Configurational Density Functional Theory: Progress and Challenges
Hedegård Erik Donovan,
Hedegård Erik Donovan
Division of Theoretical Chemistry, Lund University, Kemicentrum P.O. Box 124, SE-221 00 Lund, Sweden
Search for more papers by this authorHedegård Erik Donovan,
Hedegård Erik Donovan
Division of Theoretical Chemistry, Lund University, Kemicentrum P.O. Box 124, SE-221 00 Lund, Sweden
Search for more papers by this authorBook Editor(s):Leticia González,
Roland Lindh,
Leticia González
Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Austria
Search for more papers by this authorRoland Lindh
Department of Chemistry – BMC, Uppsala University, Sweden
Search for more papers by this author*Electronic mail: [email protected]
Summary
Kohn-Sham density functional theory (KS-DFT) in its time-dependent (linear response) formulation has often provided accurate accounts of electronic excitations and excited state processes. The main features of DFT and its linear response variant are a cost efficient and quite accurate description of dynamical correlation, which is a large challenge for methods based on traditional wave function theory. However, DFT also has limitations, e.g., electronic states where several configurations are of importance; a scenario often encountered for electronically excited states. For these cases a correct description requires a genuine multi-configurational ansatz. The high computational cost of multi-configurational methods has, however, been a large hindrance for their general usage. This has led to development of a number of methods combining DFT and multi-configurational wave functions. The goal is to let the multi-configurational wave function include the configurations required for a physically correct description of the electronic state, while DFT efficiently can recover the dynamical correlation. In this chapter we provide an overview of different methods, combining multi-configurational wave functions and DFT. We discuss the main challenges with outset in three different models namely MRCI/DFT, MC-PDFT and MC-srDFT. These three models have been applied to describe excited states of a large number of organic molecules and to a lesser degree also transition metals; hence an preliminary assessment of their performance for chemically different systems can be made.
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