$Ab initio$ prediction of Vibrational Circular Dichroism beyond the harmonic approximation.

Recently, vibrational circular dichroism (VCD), $i.e.$, CD in the IR, supported by Density Functional Theory calculations has gained considerable success in assigning the absolute configuration and in evaluating the conformational properties and supramolecular interactions of chiral molecules. Inclusion of the anharmonic treatment is often still overlooked, but is mandatory to investigate some spectral regions ($i.e.$, NIR). Indeed, taking into account anharmonicity up to second-order vibrational perturbation theory allows treating combination and overtone bands both considering frequencies and intensities, that is dipole and rotational strengths. Due to the presence of resonances (Fermi and Darling-Dennison ones) and large amplitude motions, calculations for large and flexible systems still remain challenging and $ad hoc$ protocols are needed. From simple alcohols to natural products to chiral astrochemical molecules, in this contribution we will present some tools to sustain anharmonic calculations allowing direct comparison with the experimental spectra.