Optimized diatomics-in-molecules potential energies for H3 and H4

Abstract

Several variants of diatomics‐in‐molecules (DIM) theory are used to calculate the potential‐energy hypersurfaces (PEH) for H₃ and H₄. The minimum basis set calculations yield qualitatively incorrect PEHs for these systems. Extension of the basis set to include the excited ²S* state or ionic states of hydrogen can result in a good ’’optimized’’ DIM PEH for H₃, but the H₄ energies remain poor. Extension of the theory to include triatomic contributions explicitly does not correct the H₄ energies in the minimum basis set application.