  The adsorption of rare gases on metal surfaces serve as the paradigm of weak
adsorption where it is typically assumed that the adsorbate occupies maximally
coordinated hollow sites. Density-functional theory calculations using the
full-potential linearized augmented plane wave method for Xe adatoms on
Mg(0001), Al(111), Ti(0001), Cu(111), Pd(111), and Pt(111), show, however, that
Xe prefers low-coordination on-top sites in all cases. We identify the
importance of polarization and a site-dependent Pauli repulsion in actuating
the site preference and the principle nature of the rare-gas atom--metal
surface interaction.
