Estimates of some molecular relativistic energies from single-centre expansions

The ‘molecular puff’ equations are set up within the Hartree-Fock and relativistic Hartree-Fock frameworks, and solved by direct integration for a number of hydrides of the first, second, third and fourth rows. From the solutions of these equations a priori estimates of the relativistic energies are obtained. These are shown to vary from 1–2 ev for the first row hydrides to nearly 200 atomic units for HI.