Molecular Interactions in Particular Van der Waals Nanoclusters

A method is presented to analyse the interaction energies in a nanocluster, which is consisting of three neutral molecules bound by non-covalent long range Van der Waals forces. One of the molecules (M-0) in the nanocluster has a permanent dipole moment, whereas the two other molecules (M-1 and M-2) are non-polar. Analytical expressions are obtained for the numerical calculation of the dispersion and induction energies of the molecules in the considered nanocluster. The repulsive forces at short intermolecular distances are taken into account by introduction of damping functions. Dispersion and induction energies are calculated for a nanocluster with a definite geometry, in which the polar molecule M-0 is a linear hydrocarbon molecule C5H10 and M-1 and M-2 are pyrene molecules. The calculations are done for fixed distances between the two pyrene molecules. The results show that the induction energies in the considered three-molecular nanocluster are comparable with the dispersion energies. Furthermore, the sum of induction energies in the substructure (M-0, M-1) of the considered nanocluster is much higher than the sum of induction energies in a two-molecular nanocluster with similar molecules (M-0, M-1) because of the absence of an electrostatic field in the latter case. This effect can be explained by the essential intermolecular induction in the three-molecular nanocluster.