Long-Range Intermolecular Forces using Gaussian Basis Functions. A Model Calculation

The charge-induced dipole induction energy and the dipole–dipole dispersion energy for the ground state H–H+ and H–H interactions are used as model energies for investigating the feasibility of using Gaussian basis functions to calculate long-range intermolecular forces. The use of various types of Gaussian basis sets to represent the first-order wavefunction, Ψ(1), in the calculation of the interaction energies and the errors introduced into the calculations by using Gaussian representations of the exact zeroth-order wavefunctions for the isolated atoms are considered. Satisfactory long-range forces, at least for the simple interactions considered here, can be obtained by using small Gaussian basis sets to represent the interaction, that is Ψ(1), and/or the zeroth-order wavefunction.