Retreating monomolecular step

Figure 2. A retreating monomolecular step on the [100] surface of an oxide mineral with the rocksalt structure, such as MnO(s). Numbers identified in the wireframe diagram indicate the coordination numbers of oxygens to metal i.e., the number 4 identifies a P4-0XO site.

FIG. 5 The retreating monomolecular step NiO(s) from Fig. 2 shown with the changed coordination number of oxygens in the inset. The co-ordination sphere of the metals is maintained by movement and dissociation of water molecules to re-establish a steady-state surfece. 

Figure 1. An atomic-force microscope image showing monomolecular steps being generated at a dislocation on the surface of calcite (image courtesy of R. Shiraki, T. Land and P. Rock). The steps grow and retreat as mass is accumulated or lost at these steps.

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