Full-variational treatment of GTF basis sets for molecular orbitals: application to interactions in the helium dimer under an electrostatic field

The full-variational optimization method at the SCF and MP2 levels is appli ed to a calculation of the intermolecular interaction energy of the helium dimer under an electrostatic field. The results under an external field sho w that the basis set superposition errors are suppressed by this method and that the intermolecular interaction energies calculated with s functions o nly are comparable to those of conventional calculations with polarization functions. (C) 1998 Elsevier Science B.V. All rights reserved.