Simple model for work-function changes due to adsorption by metals

We develop an analytical method for dealing with the work-function change due to adsorption by metals. A trial function is used for obtaining the electron distribution which gives the minimum of the Hohenberg and Kohn energy functional for the inhomogeneous electron gas of an adsorbate-substrate system. It is shown that this method yields results which reasonably approximate those obtained by Lang's numerical method, especially for dilute adsorptions. If an effective valence equal to four is employed for tungsten substrate (i.e., $r_s=1.85\mathrm{}$ a.u.), results calculated by this method are in sufficient agreement with experimental data for adsorptions of metals having monolayer thickness less than ∼ 6 a.u. Using this model, the mechanism of work-function change is discussed.