Anomaly in the anisotropy of the aluminum work function

Ab initio calculations combined with a recently developed macroscopic-averaging technique have been used to examine the anisotropy of the aluminum work function. Our results indicate that the Al(111) work function is substantially lower than the Al(100) work function, and slightly below the Al(110) work function. This is in contrast to other fcc metals, for which a (110)→(100)→(111) increasing trend is observed experimentally and predicted by Smoluchowski's rule. We show that the aluminum work-function anomaly, which is in agreement with experiment, is due to the increased p-atomic-like character of the density of states at the Fermi energy, as compared to most other fcc metals.