Interaction of small aromatic molecules: An ab initio studies on benzene and pyridine molecules

The use of appropriate level of theories for studying weak interactions such as stacking of aromatic molecules has been an important aspect, since the high level methods have limitations for application to large molecules. The differences in the stacking energies of various structures are found significant for identifying the most favored stacked benzene rings and the pyridine rings. The most favored structure of benzene rings obtained from various methods are similar, and also comparable with that of reported accurate CCSD(T) method. The effect of basis set in the stacking energies of MP2 calculations is small. Thus the moderately accurate methods may be feasible for studying the stacking interactions as demonstrated for benzene and pyridine molecules.