Surf. Sci. 360, L499 (1996)
S. Andersson and M. Persson
Dep of Applied Phys., CTH/GU, Göteborg
J.
Harris
Biosym Technologies Inc., San Diego
The crystal face dependence of the physisorption energies for H_2 and D_2 interacting with low-index faces of Al and Cu has been measured. The effect is pronounced for Al. The data show that the (111) and (110) faces of Al display similiar potential well-depths, larger by 40 % than the well-depth for the intermediate (100) face.We discuss this surprising result in the light of conventional theoretical models and show, in particular, that these fail to take account of important non-asymptotic effects in the face dependent electron density profiles.