Alkali halide surfaces: Potential energy surfaces for diffusion and dimer dissociations

Abstract

We report results from electrostatic calculations of activation barriers for surface motions of alkali halides adsorbed on alkali halide (100) crystal faces. The results include energy surfaces for adsorbate diffusion along single‐step ledges and dimer motions at idealized kink defects. Activation barriers for diffusion and desorption along the crystal surface and ledges are nearly equal, which implies that the pre‐exponential factors for both rates are significant in determining diffusion distances for adsorbates. Dimer motions at kink defects either interconvert several possible stable isomers or lead to diatomic dissociation products. The kink’s role in such movements is to distort the different dimer configurations and to strongly bond one diatomic pair during dissociation. There is a direct relationship between the structure of the adsorbed dimer and the diatomic products formed from specific dimer motions.