Electronic and elastic contributions in the enhanced stability of Ge(1 0 5) under compressive strain

Accurate first principles calculations reveal that a huge inward relaxation turns the originally stepped Ge(1 0 5) surface into a flat one, with surface energy equal to the Ge(0 0 1)p(2 × 2) at the bulk lattice parameter. Under in-plane compression (up to 4%) the surface energy of the (1 0 5) gets sizably lower than the (0 0 1), because of a combination of the elastic contribution provided by stretched dimers at the rebonded steps and the dangling-bond energy lowering generated by enhanced tilting of these dimers.