Augmenting basis set for time-dependent density functional theory calculation of excitation energies: Slater-type orbitals for hydrogen to krypton

Attention is given to the dual nature of the time-dependent density functional theory approach for predicting excitation spectra, namely its theoretical basis in dynamic polarizability and its practical implementation in computer programs as a single configuration interaction. A procedure for generating diffuse functions to be added to standard Slater-type orbital basis sets for H to Kr is proposed and tested on ten close-shell molecules. The database for comparing the performance of standard and augmented basis sets consists of the 15 lowest transitions to valence and Rydberg-like states for each of the molecules. The results of this computational study are very encouraging. The addition of new augmenting functions improves the performance of standard basis sets significantly. For example, the new augmented TZP basis set, about the same size as the standard TZ2P set (and considerably smaller than the large QZ4P set), led to an average absolute deviation of 150 predicted excitation energies of only 0.12 eV from those obtained with the very large basis set called QZ3P-3DIFFUSE, compared to 0.83, 0.79, and 0.19 eV, for the standard TZP, TZ2P, and QZ4P sets, respectively. Similar augmenting functions for Gaussian-type orbital basis sets for H to Kr are also suggested.