This chapter gives, in section 6.1, some generally accessible models of metallic behavior, and tabulates the values of work function and surface energies of selected metals. In section 6.2 we discuss electron emission properties of metals, concentrating on the role of low work function, high surface energy materials as electron sources; we also show that electron emission and secondary electron microscopy can be used to study diffusion of adsorbates. An introduction to magnetism in the context of surfaces and thin films is given in section 6.3.

The electron gas: work function, surface structure and energy

Free electron models and density functionals

Free electron models of metals have a long history, going back to the Drude model of conductivity which dates from 1900 (Ashcroft & Mermin 1976). The partly true, partly false predictions of this classical model were important precursors to quantum mechanical models based on the Fermi–Dirac energy distribution. If words in the following description don't make sense, now is the time to take a second look at section 1.5. Modern calculations start from a description of the electron density, ρ−(r) (ρ−(z) in 1D) in the presence of a uniform density ρ+(r or z) of metal ions. This is the jellium model, where the positive charge is smeared out uniformly. At a later stage we can add the effects of the ion cores Δρ+(r) by pseudopotentials or other approximations.