Editing Work function (section)

=== Theoretical models of metal work functions ===
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Theoretical modeling of the work function is difficult, as an accurate model requires a careful treatment of both electronic [[many-body problem|many body effects]] and [[surface chemistry]]; both of these topics are already complex in their own right.

One of the earliest successful models for metal work function trends was the [[jellium]] model,<ref>{{Cite journal | last1 = Lang | first1 = N. | last2 = Kohn | first2 = W. | doi = 10.1103/PhysRevB.3.1215 | title = Theory of Metal Surfaces: Work Function | journal = Physical Review B | volume = 3 | issue = 4 | pages = 1215 | year = 1971 |bibcode = 1971PhRvB...3.1215L }}</ref> which allowed for oscillations in electronic density nearby the abrupt surface (these are similar to [[Friedel oscillation]]s) as well as the tail of electron density extending outside the surface. This model showed why the density of conduction electrons (as represented by the [[Wigner–Seitz radius]] ''r<sub>s</sub>'') is an important parameter in determining work function.

The jellium model is only a partial explanation, as its predictions still show significant deviation from real work functions. More recent models have focused on including more accurate forms of [[electron exchange]] and correlation effects, as well as including the crystal face dependence (this requires the inclusion of the actual atomic lattice, something that is neglected in the jellium model).<ref name="venables"/><ref>{{cite book | isbn = 9780080536347 | title = Metal Surface Electron Physics | last1 = Kiejna | first1 = A. | last2 = Wojciechowski | first2 = K.F. | date = 1996 | publisher = [[Elsevier]]  }}</ref>