Studies of the Interaction between Stable Molecules and Atoms. III. A Molecular Orbital Treatment of the Quadratic Form of H4

Abstract

Molecular orbital calculations of the quadratic arrangement of four hydrogen atoms have been carried out as a function of the internuclear distance. It is shown that the complex has orbital degeneracy in the ground state. An approximation, which includes the lowest orbital and the degenerate orbitals only, yields a triplet and three singlet states, the triplet being the lowest one in accordance with Hund's rule. The actual calculations show that the quadratic H₄ is unstable with respect to a totally symmetrical displacement at all points of the potential energy surface.