TDDFT in material science; Application for dual fluorescent molecules
Over the last decade, Density Functional Theory (DFT) has become one of the
major tools in modern quantum chemistry. It has been included in
methods (Car-Parrinello) as well as in QM/MM hybrid techniques.
The development of Time-Dependent Density-Functional Theory (TDDFT) as a
rigorous formalism within DFT has been a major step, opening the possibility
calculate exited states of simple molecules and large systems with an accurate
precision at low computational cost.
TDDFT results usually surpass those of time dependent Hartree-Fock or
Configuration Interaction with Single excitation (CIS) and are more comparable
in quality to those obtained with ab initio methods.
A TDDFT investigation of Charge Transfer Excited States is presented,
the phenomenon of dual fluorescence of compounds of the same family as 4-(N,N
dimethylamino)benzonitrile molecules. A classification of the studied
in four classes is proposed based on the Twisting Intramolecular Charge
Transfer model. This classification based on the form of the calculated
potential energy surfaces of the ground and excited states allows to
understand the different fluorescent behaviour of these molecules.
Influence of various functionals and future developments are discussed.