The atomic structure of (2 5 11), a previously unknown stable surface, was determined by means of in situ scanning tunnelling microscopy and first-principles electronic structure calculations. This orientation was located within the stereographic triangle. That is, far from all low-index surfaces. A low-energy (1 x 1) reconstruction which contained As dimers formed on the surface. Analysis of the surface structure showed that, for semiconductor surfaces, the gain in stability due to minimization of the number of dangling bonds was more important than the gain of creating a semiconducting ground state.

GaAs(2 5 11): a New Stable Surface within the Stereographic Triangle. L.Geelhaar, J.Márquez, P.Kratzer, K.Jacobi: Physical Review Letters, 2001, 86[17], 3815-8