Periodic States in the Constrained Equilibrium of Vicinal Nb (011) Miscut along [100]

At a temperature of 1700 K the Nb (011) vicinal surface miscut along $[100]$ is observed by low energy electron microscopy to be almost ideal, with single step edges of unit height. Below 1560 K, step edges coalesce to form a surface entirely of 110 facets. In between these temperatures we observe states in which facets and dissociated steps alternate, to form periodic structures. For a simplified model these states form a stable phase in the constrained equilibrium of the vicinal surface.