Influence of relaxation on the size distribution of monatomic Ag chains on the steps of a vicinal Pt surface

Recently, Gambardella et al. [Phys. Rev. B 73, 245425 (2006)] determined experimentally the size distribution of the chains of Ag atoms self-assembled on the steps of a vicinal Pt surface. The experimental results were interpreted by the authors within a simple model which predicted the monotonous distribution of the chain sizes. The data, however, exhibit a nonmonotonous behavior with a maximum. We show that if additional interactions unaccounted for in the model introduce a sufficiently large positive curvature of the chain energy, the size distribution can be fitted to the experimental data with high accuracy. We discuss several interactions which may provide the necessary curvature.