Accuracy of DFTB for the prediction of photo-absorption spectra

Recently, our group presented a new way to represent orbital confinement for the calculation of Slater-Koster tables for use in density functional tight binding (DFTB) models (Jenness et al., J. Chem. Theory Comp. 16, 6894 (2020)). By applying the confinement term on a per-orbital basis, as opposed to the per-atom basis of standard DFTB, we demonstrated that an improved description of molecular topologies is achieved. In the current study, we seek an understanding of how these orbital dependent confinement terms are able to predict excited state properties as exemplified by photo-absorption spectra. Herein, we compare results from our novel DFTB model and standard DFTB model with time-dependent density functional theory and equation of motion coupled cluster in order to determine the influence of our orbital dependent scheme on this critical chemical phenomena.