Deriving accurate work functions from thin-slab calculations

Quantum-size effects have been shown to influence significantly the determination of work functions from thin-slab calculations. We show here that a technique based on macroscopic averages can be used to reduce such effects and determine more precisely the work functions of metals from ab initio thin-film calculations. The technique combines the mean electrostatic potential step across the slab surface with the Fermi energy of a bulk crystal. The method is applied to Al(100) slabs containing 1-14 atomic layers.