Semiclassical vibrational spectroscopy : the importance of quantum anharmonicity in supra-molecular systems

Semiclassical (SC) vibrational spectroscopy has been applied successfully to several molecular systems thanks to the possibility to regain quantum effects accurately starting from short-time classical trajectories.[1-5] Larger molecular and supra-molecular systems represent instead an open challenge in the field of semiclassical spectroscopy mainly due to the necessity to work in very high dimensionality. To start off the talk I will present some recent theoretical advances able to extend the range of applicability of SC vibrational spectroscopy to very high-dimensional systems.[6-7] Then, I will move to applications of semiclassical spectroscopy concerning the vibrational features of water clusters and two supra-molecular systems involving glycine.[8-9] These applications will point out the importance of a multi-reference, dynamical approach able to reproduce quantum anharmonicities without employing any ad-hoc scaling factor. [1] M. F. Herman, E. Kluk, Chem. Phys. 1984, 91, 27. [2] A. L. Kaledin, W. H. Miller, J. Chem. Phys. 2003, 118, 7174. [3] M. Ceotto, S. Atahan, G. F. Tantardini, A. Aspuru-Guzik, J. Chem. Phys. 2009, 130, 234113. [4] R. Conte, A. Aspuru-Guzik, M. Ceotto, J. Phys. Chem. Lett. 2013, 4, 3407. [5] F. Gabas, R. Conte, M. Ceotto, J. Chem. Theory Comput. 2017, 13, 2378. [6] M. Ceotto, G. Di Liberto, R. Conte, Phys. Rev. Lett. 2017, 119, 010401. [7] G. Di Liberto, R. Conte, M. Ceotto, J. Chem. Phys. 2018, 148, 014307. [8] G. Di Liberto, R. Conte, M. Ceotto, J. Chem. Phys. 2018, 148, 104302. [9] F. Gabas, G. Di Liberto, R. Conte, M. Ceotto, to be submitted.