A benchmark study of electronic excitation energies, transition moments, and excited-state energy gradients on the nicotine molecule.

In this work, we report a comparative study of computed excitation energies, oscillator strengths, and excited-state energy gradients of (S)-nicotine, chosen as a test case, using multireference methods, coupled cluster singles and doubles, and methods based on time-dependent density functional theory. This system was chosen because its apparent simplicity hides a complex electronic structure, as several different types of valence excitations are possible, including n-π(*), π-π(*), and charge-transfer states, and in order to simulate its spectrum it is necessary to describe all of them consistently well by the chosen method.