ANISOTROPIC ELASTIC ANALYSIS AND ATOMISTIC SIMULATION OF ADATOM-ADATOM INTERACTIONS ON SOLID SURFACES

We employ atomistic computer simulations and anisotropic elastic analysis to investigate the nature of adatom-adatom interactions on solid surfaces. Point dipole forces are used to model the elastic field generated by adatoms on a surface. In agreement with previous results, the anisotropic elastic theory shows that the adatom-adatom interaction energy has a strong angular dependence and can change sign with angle. Atomistic simulations are used to test the validity of the anisotropic elastic theory and to determine the overall magnitude of the dipole force, which is needed to fully parameterize the elastic theory. These simulations are performed for Ni adatoms on a {001} Ni substrate using Embedded-Atom-Method (EAM) interatomic potentials. The simulations are shown to be in very good agreement with the anisotropic elastic theory prediction. However, when the spacing between adatoms is small, dipole-quadropole interaction terms become important, especially in directions in which the dipole-dipole interactions are very small. The magnitudes of the force dipole, determined from simulations that emphasize different crystallographic directions, are all nearly identical. This further supports the anisotropic dipole-dipole interaction model for adatom interactions on solid surfaces.