Description of Intermolecular Interactions in (CH4)2, CH4Ne, and Ne2 Dimers

The comparative ab initio study of intermolecular interactions in methane–methane, neon–neon, and methane–neon dimers is carried out by using the coupled cluster method with consideration for single and double excitations and the noniterative correction for triple excitations (CCSD(T)) with Dunning basis sets complemented with bond functions, as well as the explicitly corelated coupled cluster method (F12-CCSD(T)). It is shown that, for the methane dimer, the mean spherical pair electron density constructed by the coupled cluster method has a minimum in its geometric center only if the set of bond functions localized in this area is used. Such a result substantiates the inclusion of intermolecular electron correlation for the basis sets of wave functions complemented with bond functions. The analysis of constructed sections of the potential energy surface (PES) makes it possible to calibrate the set of bond functions and refine the value of interaction energy for the neon dimer.