Estudo computacional das interações intermoleculares do tipo O-H...π em pequenos complexos com água

Abstract

The study of weakly bound intermolecular systems involving polycyclic aromatic hydrocarbons (PAH`s) and water agglomerates has opened new perspectives for a better understanding of the mechanisms of formation of aggregates in interstellar regions. In the special, for the understanding of the initial process of ice formation at cold molecular clouds. In this dissertation, we investigate three intermolecular complexes of water with aromatic molecules: (i) benzene-water 1:1, (ii) naphathalene-water dimer; and (iii) acenaphthylene-water trimer. We use as a theoretical procedure ab initio methods and density functional theory (DFT). Initially, to establish an appropriate methodology for the problem, we carried out one benchmark for the benzene-water system. In this case, we employ different density functionals containing dispersion corrections (DFT-D) e with non-local exchange energy (HMDFT), combined with atomic bases containing polarization and diffuse functions. Our results were compared with these obtained via perturbative methods. Subsequently, we studied geometric, energetic, vibrational aspects and kinect parameters of the naphathalene-water dimer and acenaphthylene-water trimer with DFT-D and HMDFT. Our targets have consisted of investigating the structural mobility of small water aggregates in the presence of PAH´s, evaluate the impact of the formed interaction in molecular properties (e.g dipole moment, Raman scattering of the fundamental modes) and evaluate the reorientational kinects of these complexes.