Département de chimie moléculaire

The classic d.-functional theory (DFT) formalism introduced by Hohenberg, Kohn, and Sham in the mid-1960s is based on the idea that the complicated N-electron wave function can be replaced with the math. simpler 1-electron charge d. in electronic structure calcns. of the ground stationary state. As such, ordinary DFT cannot treat time-dependent (TD) problems nor describe excited electronic states. In 1984, Runge and Gross proved a theorem making TD-DFT formally exact. Information about electronic excited states may be obtained from this theory through the linear response (LR) theory formalism. Beginning in the mid-1990s, LR-TD-DFT became increasingly popular for calcg. absorption and other spectra of medium- and large-sized mols. Its ease of use and relatively good accuracy has now brought LR-TD-DFT to the forefront for this type of application. As the no. and the diversity of applications of TD-DFT have grown, so too has our understanding of the strengths and weaknesses of the approx. functionals commonly used for TD-DFT. The objective of this article is to continue where a previous review of TD-DFT in Vol. 55 of the Annual Review of Phys. Chem. left off and highlight some of the problems and solns. from the point of view of applied phys. chem. Because doubly-excited states have a particularly important role to play in bond dissocn. and formation in both thermal and photochem., particular emphasis is placed on the problem of going beyond or around the TD-DFT adiabatic approxn., which limits TD-DFT calcns. to nominally singly-excited states. [on SciFinder(R)]