The chemical nature of electron waves in metals — A basis for the study of heterogeneous catalysis

The tight-binding method is used to describe the electronic waves of metals in the atomic orbital language familiar to chemists. It is shown that (in both fcc and bcc crystals) k vectors with components (0, 0, 1) or (1, 1, 1) carry hybrids between the s waves and Z² waves whose axis Z is parallel to the direction of the wave vector. In particular the higher-energy hybrid waves are strongly pointed along the wave vector direction. Furthermore, using the finite cube model, with excellent analytical approximations to the orbitals, the existence of privileged wave vector directions perpendicular to the surface approached by an incoming substrate is demonstrated. A preliminary discussion of the favorable conditions for catalysis emphasizes the extremely favorable role of such pointed hybrids if their sub-band lies (empty) just above the Fermi level of the metal.