A harmonic lattice model for an adatom at the (001) surface of a cubic
crystal is developed, based on the concept of eigenstrains. In this c
ontext, eigenstrains represent the distortion introduced by the adatom
, affecting the substrate atoms in its vicinity. The distortions which
model the relaxations associated with an adatom are obtained directly
using embedded atom method (EAM) potentials. The eigenstrains are tra
nslated into a set of forces which, in the case of second-neighbor int
eractions, are applied to five 'substrate' atoms in the immediate vici
nity of the adatom. Four of these atoms are located at the surface and
one in the first layer below the surface. The resulting set of forces
is self-equilibrated as expected by the nature of the adatom. The ela
stic field of the adatom is described and the limitations of the conti
nuum theory are discussed. Calculations of the interaction energy betw
een adatoms indicate agreement with existing, long-range results. The
strength of the leading singularity of the interaction energy changes,
however, when the adatoms are closely spaced. Anisotropy plays a sign
ificant role in this process; in certain directions, identical adatoms
actually attract each other. Independent simulations using EAM potent
ials clearly demonstrate the accuracy of the elastic field produced by
the eigenstrain model. The restrictive assumptions regarding the adat
om/force system found in existing models are removed in this distortio
n-based model. The eigenstrain approach can also be used to represent
surface steps and vacancies. (C) 1998 Elsevier Science Ltd. All rights
reserved.