Reaction paths on the H4 potential energy surface

Abstract
Portions of the electronic potential energy surface corresponding to various nuclear geometries of the H4 molecular system have been studied. The variational calculations employed double‐zeta basis sets (1s and 1s′ Slater‐type orbitals on each center) to form configuration interaction wavefunctions. At selected points on the surface, the effects of exponent optimization and increased basis set size (1s, 1s′, and 2p orbitals per center) were assessed. A low energy reaction path allowing a bimolecular mechanism for exchange, requiring less energy than a single H2 dissociation, was not found. However, a path leading from trapezoidal to linear structures (and vice versa) was found to offer the possibility of exchange with less than 6 kcal/mole of energy above this dissociation limit.