The computation of electronic excitation spectra has now become possible for large molecules, via efficient implementations of time-dependent density functional theory (TDDFT) and the singles and approximate doubles coupled-cluster model (CC2). In this workshop, these methods are introduced as implemented in the program Turbomole. No prior experience with Turbomole will be needed.

Despite its name, the most common usage of TDDFT is to compute excited state properties within the linear response framework. In this case of excitation energies, no time dependence in modelled. CC2 is an alternative to TDDFT for computing excitation energies on large systems. It is not as efficient as TDDFT (yet, at least), but quite large systems can already be treated. Of the wave function based methods of computing excitation energies, it has, arguably, the best price/performance ratio.