Naphthalene dimer and naphthalene dimer with Ar: calibration calculations and the effect of Ar on the stability and vibrational frequencies

The harmonic vibrational frequencies of naphthalene and its dimers are computed using density functional theory including an empirical correction for dispersion. The C-H out-of-plane bending modes in the naphthalene dimers show a red or a blue shift depending on the relative orientation of the two naphthalene molecules. The addition of Ar atoms does not significantly affect the vibrational frequencies, but changes the energy separation between the two dimer conformations.