Investigating molecular quantum vibrational frequencies with semiclassical dynamics: theory and application to systems of astrochemical interest

Semiclassical (SC) dynamics allows to regain quantum effects starting from short-time classical trajectories. This feature makes it an attractive and promising tool for accurate spectroscopy investigations, which cannot neglect quantum effects. To start off I will briefly review the main SC approaches employed in vibrational spectroscopy including very recent advances to extend the range of applicability of SC dynamics to large molecular and supra-molecular systems.[1-6] Then, I will present an application of the SC theory to the astrochemically relevant glycine molecule.[7] Finally, the semiclassical study of supra-molecular systems involving glycine will demonstrate the importance in vibrational spectroscopy of an approach able to account for quantum anharmonicity over the commonly employed procedures based on an ad hoc scaling of the harmonic frequencies. 1. M. F. Herman and E. Kluk, Chem. Phys. 91, 27 (1984). 2. A. L. Kaledin and W. H. Miller, J. Chem. Phys. 118, 7174 (2003). 3. M. Ceotto, S. Atahan, G. F. Tantardini, and A. Aspuru-Guzik, J. Chem. Phys. 130, 234113 (2009). 4. R. Conte, A. Aspuru-Guzik, and M. Ceotto, J. Phys. Chem. Lett. 4, 3407 (2013). 5. M. Ceotto, G. Di Liberto, and R. Conte, Phys. Rev. Lett. 119, 010401 (2017). 6. G. Di Liberto, R. Conte, and M. Ceotto, J. Chem. Phys. 148, 014307 (2018). 7. F. Gabas, R. Conte, and M. Ceotto, J. Chem. Theory Comput. 13, 2378 (2017).