Studies of the Interaction between Stable Molecules and Atoms. IV. The Energy of the Linear H4 Complex

Abstract

Roothaan's LCAO—SCF treatment has been applied to the linear symmetrical H₄ complex in an attempt to test this method for calculating the energies of activated complexes. Calculations have been made for internuclear distances of 1.4, 1.6, 2.0, and 2.2 a.u. The SCF method gives a lower value for the energy of 1.4 a.u. than was obtained by a simple molecular orbital method without configuration interaction, but gives a higher value than the best configuration interaction treatment. The values of the energies that were obtained are —55.48, —55.99, —56.50, and —56.54 ev at distances of 1.4, 1.6, 2.0, 2.2 a.u., respectively. The changes in the wave functions as one adiabatically changes the internuclear distance are of particular interest. Although the results cannot be directly compared with experiment, reasonable values for the energy are obtained indicating that the molecular orbital SCF method with a limited amount of configuration interaction is a promising method for treating closed‐shell molecules and interactions between such molecules for small values of the internuclear parameters.