Gas phase optical rotation calculated from coupled cluster theory with zero-point vibrational corrections from...

Molecular vibrations can have a significant influence on gas phase specific optical rotations. Mainly due to the large number of nuclear degrees of freedom in most chiral molecules, theoretical predictions of vibrational corrections quickly become prohibitively expensive. Here, we investigate an approach in which the purely electronic contribution is calculated at the coupled cluster singles and doubles level, while the zero-point vibrational correction is computed using the less demanding density functional theory (B3LYP functional). By comparing to experimental gas phase results for seven molecules and two wavelengths, we find that the mixed coupled cluster/B3LYP approach performs significantly better than pure B3LYP predictions. In fact, we find that it is more important to use high-level electron correlation for the electronic contribution than to include zero-point vibrational corrections.