 Cleavage along the (111) surface at low-temperatures results in another 2×1 reconstruction, differing from the (100) surface by forming long pi-bonded chains in the first and second surface layers.However, when heated above 400 °C this structure converts irreversibly to the more complicated 7×7 reconstruction.In addition, a disordered 1×1 structure is regained at temperatures above 850 °C, which can be converted back to the 7×7 reconstruction by slow cooling.