Study of the Structure of Monoatomic Adsorbates on Metal Surfaces Using the Sphere-in-Contact Model

We have recently shown that the sphere-in-contact model can be used as an educational and research tool in various contexts, such as the visualization of carbon structures (e.g. graphene, carbon nanotubes, carbon nanocones and graphite), heterogeneous catalysts, metal nanoparticles and organic molecules. In this communication we present how it can be used to model the adsorbate structure of a monoatomic element on the hexagonal close-packed surface of the metal. We have used atoms of varying radius to represent the metal surface atoms and the adsorbate atoms. The study reveals that many surface symmetries are possible for a fixed adsorbate coverage by the movement of the adsorbate atoms in response to surface adsorbate-adsorbate repulsions. The movement of the particles (e.g. particle diffusion) can be seen directly in the model and this is caused by the user intervention. This has great educational but also research value as one can directly see how the adsorbate atoms reorder on the surface of a metal. We believe that this model will be useful in the rational design of catalytic materials and materials coatings with new technological applications.