Dissociation energies of diatomic molecules related to equilibrium bond lengths

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Abstract
The problem of calculating dissociation energies of all but the lightest molecules remains a formidable one in quantum chemistry. However, the calculation of equilibrium internuclear distances is much simpler. Therefore, in this paper, we have explored whether the dissociation energies of diatomic molecules can be directly related to the nuclear–nuclear potential energy V n n , plus molecular invariants. These latter quantities are the total number of electrons N and the ‘‘approximate’’ invariant, the total kinetic energy of the separated atoms, denoted by T. For chemically similar series, a marked correlation of D with V n n /T is demonstrated, which for the N2, P2, etc. series can be represented approximately by D/N 1 / 2=[300(V n n /T)−6] kcal which would mean no binding above a limiting atomic number, lying higher, however, than those that span the Periodic Table. The existence of a minimum value of V n n /T in groups of chemically stable homonuclear diatomic molecules is then contrasted with the situation in chemically similar series of heteronuclear diatomic molecules. Here, no minimum value of V n n /T is found, due, it is argued, to the stabilization of these molecules by charge transfer.