An exact treatment of the induction interaction between the atoms in the hydrogen molecule

The second-order induction energy arising in the interaction of two ground-state hydrogen atoms is evaluated exactly by using the angular expansion of the relevant Green's function. This energy is interpreted as a result of the interaction of the atom a with the screened Coulomb field of the atom b and vice versa. It is shown that the induction energy, though negligible at large interatomic distances, is very important when the electronic clouds of the atoms overlap significantly. In the chemical minimum region the induction interaction of two hydrogen atoms accounts for over 90 per cent of the binding energy missing in the first-order Heitler-London calculation. Some aspects of practical evaluation of the induction energy for larger systems are also briefly discussed.