Impurity interactions and pseudo-molecule formation in metals

It is shown that the concept of molecular orbitals is a useful one also in describing interactions between impurities in metals. The conclusion is based on first principles, self-consistent calculations for H₂ in jellium. The dissociation energy is primarily determined by the position of the Fermi energy relative to an antibonding molecular resonance. In a dense metal like A? this is completely filled and the dissociation energy is an order of magnitude smaller than for free H₂.