Energy decomposition analysis of the intermolecular interaction energy between different gas molecules (H2, O2, H2O, N2, CO2, H2S, and CO) and selected Li+-doped graphitic molecules: DF-SAPT (DFT) calculations

Abstract

In the present study, the energy decomposition analysis of the intermolecular interaction energy (Eint) between different Li+-doped graphitic molecules (Li+–CxHy) and the gases such as H2, O2, N2, 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 (Eint) and its decomposed components [electrostatic (Eelec), exchange (Eexch), induction (Eind), and dispersion energy (Edisp)] 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+–C x H y molecules and the selected gases, as well as the Li+–C x H y 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 Eint 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 Eelec was nearly insensitive to the size of the graphitic substrate, especially for the H2, CO, and N2 molecules, while for the H2O showed a small dependency. Similarly, the Eexch was nearly size independent for the H2 and CO gases; however, Eexch showed some dependencies on the size of the graphitic substrate for the H2O and N2 molecules. This later dependency was higher than that of the Eelec. The variation in the Eind with the size of the desired systems for the H2O was more evident than that of the H2, N2, and CO. The dependency of the Edisp on the size of the model was less than that of the other energy components, in particular for the H2O molecule.