Ab Initio Description of the Structure and Interaction Energy of Perhalomethane Dimers

The intermolecular interactions in (CX 4 ) 2 dimers (X = H, F, Cl, Br, I) were studied by the ab initio methods. The calibration values of the energies and bond lengths of the dimers were obtained by the coupled-cluster method taking into account single and double excitations and the non-iterative correction for triple excitations (CCSD(T)) with Dunning’s basis sets complemented with bond functions centered between the carbon atoms, followed by extrapolation to the infinite basis set limit. An analysis of the constructed PES cross sections of the (CX 4 ) 2 dimers allowed us to substantially refine the dissociation energies for (CCl 4 ) 2 and (CBr 4 ) 2 from previous calculations and to evaluate the dissociation energy of the (CI 4 ) 2 dimer. The constructed correlations between the calculated dissociation energies of the (CX 4 ) 2 dimers and the polarizabilities of CX 4 revealed the critical role of polarizability of individual molecules in the variation of the physical properties of CX 4 dimers with X changed from fluorine to iodine.