TDDFT is an extension of DFT for the excited states of molecules and materials. It is useful for predicting UV-stability, the absorption energy of materials, and the fluorescence and phosphoresence of OLEDs.
TDDFT computes excited electronic states by applying a time-varying electric field to the molecule. The energies of these transitions correspond to the energies between electronic states, while the intensities indicate the relative likelihood of such transitions happening.
TDDFT can be used to compute the emission color of a molecule and various spectroscopic profiles, such as UV-Vis spectroscopy, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and x-ray absorption spectroscopy (XAS). To reproduce a molecule's exact color and profiles, TDDFT results often need to be averaged over a large number of conformers. The vibrational modes of each conformer also need to be taken into account due to thermal energy causing a broadening of the transitions. However, general trends can often be seen with a single TDDFT computation.
Photochemical processes of molecules, such as degradation due to UV, can be predicted by optimizing electronically excited states, and seeing which bonds break. Similarly, conical intersections and minimum energy crossing points (MECPs) can be obtained via TDDFT to determine the rate of relaxation between spin states. Given the broadband nature of most UV sources, it is often necessary to examine a few of the lowest energy electronic states and how they evolve after being formed.
At this time, Rowan doesn’t support TDDFT. If you are interested in running TDDFT computations with Rowan, please let us know at contact@rowansci.com.
