Semiclassical Molecular Dynamics as a useful tool for Nuclear Spectroscopy

Semiclassical Initial Value Representaiton (SCIVR) molecular dynamics has been known since a long time to be able to calculate accurately vibrational power spectra of small, isolated molecules with inclusion of quantum effects, such as zero-point energies, overtones, tunneling splittings, and quantum resonances.[1] Our group introduced some methodological advances that have permitted the application of semiclassical spectroscopy to large molecular systems, up to several dozens of atoms, and the simulation of nuclear power spectra together with the determination of vibrational eigenfunctions. In this talk I will briefly recall the SCIVR approximation and introduce the divide-and-conquer semiclassical initial value (DC SCIVR)[2] method. After this brief introduction, I will focus mainly on applications. Specifically, I will show how we implemented DC SCIVR with a machine learning algorithm and applied it to NMA spectra calculations, how SCIVR can deal with the solvation issue by studying water clusters[3] and discussing the issue of the OH band in the formic acid dimer. We also deal with molecular adsorption on TiO2(101) Anatase surface using direct ab initio molecular dynamics by reproducing spectra of adsorbed molecules.[4] Then, simulations of some relevant spectral features of nucleobases, nucleosides, solvated thymidine will be used to compare results based on precise ab initio on-the-fly semiclassical dynamics with those relying on force fields.[5,6]