Interaction Energy among Three Helium Atoms

Abstract

Molecular orbitals made up of linear combinations of atomic orbitals, as well as orbital, total, and interaction energies, have been calculated for the linear configuration of three He 1 — s atoms, with equal separation between the center and each outer atom. Roothaan's self‐consistent field matrix method was applied to this case. All electronic interactions were considered, their contributions appearing in the Hamiltonian used in solving for total energy. The assumption of additivity of the energies of all pairs of atoms in determining interaction energy is shown not to be valid for internuclear separations approaching collision diameter of the 1 — s He atom, about 1 A. Deviation from additivity, as determined using the results of Wehner's MO calculation for the system He₂ is about 30% for the smallest internuclear separation considered, around 0.93 A.