Interference of surface relaxations in unsupported thin films

Abstract
We present embedded-atom simulations of interlayer relaxations in very thin slabs of Al and NiAl with (110) and (210) surfaces. The interlayer spacing at a given depth from the surface depends strongly on the slab thickness. For example, the value of the first-layer contraction exhibits a decaying oscillation about that for a semi-infinite solid as the slab thickness is increased. These effects can be understood as an interference of the relaxations from each of the two free surfaces of the slab. This interference model provides quantitative predictions of the slab interlayer spacings.