Incremental DF-LCCSD(T) Calculations for a Water Molecule Inside and Outside Armchair Carbon Nanotubes

Abstract

The method of increments is applied to investigate the adsorption of a single water molecule inside and outside armchair carbon nanotubes with different curvature using density-fitting local coupled cluster with single and double excitations and perturbative triples treatment (DF-LCCSD(T)). The correlation contribution to the adsorption energy is expanded in terms of localized orbitals of both the water molecule and the nanotube. Results of this investigation show that the simultaneous correlation of groups of localized orbitals of the water molecule and of the carbon nanotube (i. e. inter-fragment two-body increments) is the major contribution to the attractive interaction. In contrast the individual correlation energy of localized orbitals of water molecule or carbon nanotube (i. e. one-body increments) is negligible. A detailed balance between the repulsive Hartree-Fock contribution and the attractive correlation contribution to the adsorption energy determines the ground-state structure of the water molecule inside the carbon nanotube. To elucidate this behavior benzene-based model systems are investigated with the same methods.