Abstract
The equilibrium geometries and binding energies of the van der Waals (vdW) complexes benzene–neon and benzene–argon have been calculated at the level of second-order Mo/ller–Plesset perturbation theory (MP2). Terms linear in the interelectronic distances r12 were used in the MP2 treatment to converge fast to the one-particle basis set limit. This new method, MP2-R12 as implemented in the sore program, was applied with high quality basis sets derived from Dunning’s aug-cc-pVXZ (X=D,T,Q,5) sets. In reward of the efforts to reach the basis set limit, it is found that the calculated binding energies for the vdW complexes were computed virtually free of a basis set superposition error (BSSE). The key MP2-R12 results are De=154 cm−1 and re=3.32 Å for benzene–neon and De=553 cm−1 and re=3.41 Å for benzene–argon. The permanent dipole moments of the vdW complexes have been computed by finite field perturbation theory. Coupled-cluster calculations of type CCSD(T), although performed with considerably smaller basis sets than the MP2-R12 calculations, show that, to improve the MP2-R12 results, it is inevitable to consider correlation effects due to connected triple excitations which go beyond the MP2 description.
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