Quantum mechanical guides to the potential energy curves of some simple molecules

The molecular orbital expression for the bond energy of a chemical bond is used to obtain some insight into the factors which produce the potential energy curves of a number of simple bonds. The resulting picture of bond formation and the potential energy curve is an electrostatic one and it depicts the potential energy curve as the sum of a long range attractive curve and a short range repulsive one. Broadly speaking, that part of the curve to the long bond length side of the minimum is determined essentially by the two electrons which form the bond and, in particular, by the `binding energy' of these two electrons. The position of the minimum and the shape of the short bond length side of the curve do depend in general on the other valence electrons of the two atoms. The long range attractive curve is easily calculated but it is difficult to get the short range repulsive curve accurately. The results may prove useful in the construction of potential energy surfaces where the long bond length side of the potential energy curve is the important part.