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Ab initio calculations of Xe monolayers adsorbed on Cu(111) surfaces

The initial adsorption of xenon on Cu(111) surfaces occurs into hexagonal monolayers, which at temperatures around 77K form a (√ 3×√ 3)R30&ordm ; ; ; commensurate structure. There has been considerable interest in the properties of this system, in particular concerning the contribution of chemisorptive bond to the overall adsorption energy. We have performed ab initio density functional calculations of the system and determined the equilibrium distances, force constants, and adsorption energies. We have found that DF calculations with the GGA functional, to which the Van der Waals interaction is explicitly added, give excellent agreement with experiment. The chemisorptive bonding is important in determining the equilibrium distances and force constants, but contributes comparatively little to the binding energy of both Xe-Xe and Xe-Cu bonds. The use of the asymptotic form of the Van der Waals interaction appears appropriate, but the position of the image plane of the metal must be carefully evaluated. We find a small preference for the on-top adsorption site, in agreement with experiment.

Density functional calculation; Van der Waals interaction; Xenon; adsorption

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