Energy decomposition analysis of the intermolecular interaction energy between different gas molecules (H-2, O-2, H2O, N-2, CO2, H2S, and CO) and selected Li+-doped graphitic molecules: DF-SAPT (DFT) calculations

摘要

In the present study, the energy decomposition analysis of the intermolecular interaction energy (E-int) between different Li+-doped graphitic molecules (Li+-CxHy) and the gases such as H-2, O-2, N-2, CO, H2S, and H2O was performed using the density fitting-density functional theory-symmetry-adapted perturbation theory [DF-SAPT (DFT)] method. The size effect of the graphitic molecule and its aromaticity on the interaction energy (E-int) and its decomposed components [electrostatic (E-elec), exchange (E-exch), induction (E-ind), and dispersion energy (E-disp)] were studied. Also, the second- order perturbation energy analysis of the Fock matrix in NBO basis was performed on all desired dimers, consisting of Li+-CxHy molecules and the selected gases, as well as the Li+-CxHy substrate alone. The aim was to investigate the relation between the charge transfer and (charge) delocalization from the graphitic substrate to the Li+ with the size of the graphitic structures in the presence and absence of the interaction. The calculations showed that the E-int between the Li+-doped graphitic molecules and the gases does not show considerable changes with the size of the graphitic substrate for all selected gas molecules. Also, the value of the E-elec was nearly insensitive to the size of the graphitic substrate, especially for the H-2, CO, and N-2 molecules, while for the H2O showed a small dependency. Similarly, the E-exch was nearly size independent for the H-2 and CO gases; however, E-exch showed some dependencies on the size of the graphitic substrate for the H2O and N-2 molecules. This later dependency was higher than that of the E-elec. The variation in the E-ind with the size of the desired systems for the H2O was more evident than that of the H-2, N-2, and CO. The dependency of the E-disp on the size of the model was less than that of the other energy components, in particular for the H2O molecule.