Adsorbate-atom-induced relaxation of thin Li(001) films.

Abstract

First-principles calculations are used to study the effects that adsorbate atoms (Li, Na, Mg, Al) have on the (001) surface of thin body-centered-cubic Li films. The Li, Na, and Mg adsorbates induce a shallow hole on the surface of the substrate at the adsorption site. The Al adsorbate, however, creates a low bump at the adsorption site. For the isolated Li adsorbate the induced surface relaxation of the substrate extends up to second neighbors from the adsorption site. The adsorbed Li atom is able to push its way closer to the surface if the number of atomic layers of the substrate film is increased from 3 to 5. If the distance between the two Li adsorbates is 3a (a=lattice parameter of the substrate), both adsorbate atoms lie in their own, completely separate, adsorption holes. When the distance between the adsorbates is decreased to 2a, the adsorption holes are merged to form a common adsorption valley. \textcopyright{} 1996 The American Physical Society.