DFT-steric-based energy decomposition analysis of intermolecular interactions

Application of a novel energy decomposition analysis (EDA) based on the recently introduced density functional theory (DFT) steric analysis is presented. The method is compared with results from the constrained space orbital variations (CSOV) and Bader's quantum theory of atoms in molecules (QTAIM) topological analysis. These two analyses explain the driving forces for the formation of dimers from different perspectives. The components of the DFT steric analysis are shown to have good linear relationships with the total interaction energy for hydrogen-bonding dimers. It is observed that some components from the new EDA method, such as steric energy, favor the formation of dimers. Moreover, comparison of the different contributions between CSOV and the DFT steric analysis provides additional insights into the physical meaning of the respective components. In addition to the total interaction energy, DFT steric energy has been found to correlate with the electron density at critical points from QTAIM analysis in different patterns for different molecular systems, which qualitatively accounts for the linear relationships between the steric and total interaction energy. The DFT steric energy is found to represent effects arising from the spatial arrangement of the electron density when dimers form, reminiscent of the steric effects invoked in chemical systems.