3.5 DFT-SAPT energy decomposition analysis
To provide further insight into the energetic origin of the intermolecular interactions, we carried out DFT-SAPT based EDA for some selected complexes. The results are summarized in Table 2. As expected, there is clear a difference between the ΔE (BSSE) andEint (SAPT) values for each complex. This is obviously due to the difference in the level of electron-electron correlation effects accounted for at each level of theory (MP2/aug-cc-VTZ and SAPT/aug-cc-pVDZ). Despite this difference, the SAPT analysis suggests that the electrostatic and polarization components of energy (Eeles and Eind , respectively) are very large and negative, contributing attractively to the overall interacting energy. This could be taken to mean that Columbic interactions play a vital role in stabilizing the equilibrium geometries of the ion-molecule complexes.