Ab Initio Calculations on the H2 + D2 → 2HD Four-Center Exchange Reaction. II. Orbitals, Contragradience, and the Reaction Surface

Abstract

We discuss the reaction surface for the four‐center exchange reaction $${\mathrm{H}}_2+{\mathrm{D}}_2\text{→ 2}\mathrm{HD}$$ in terms of the orbitals from spin‐coupling optimized GI(SOGI) calculations. The surface is comparable to previously published surfaces determined by configuration interaction. The shape of the surface is discussed in terms of the exchange kinetic energy and contragradience, which have previously been used to discuss the bonding or nonbonding of molecules.