Thermal faceting of (110) and (111) surfaces of MgO

Using LEED, we have observed the thermal faceting of MgO (110) and (111) surfaces into sets of (100) faces. Some faceting occurs under ion bombardment at room temperature, and annealing at 900–1400 K by means of electron bombardment produces complete faceting, with facets up to 1 μm across. These observations are consistent with theories of the stability of ionic crystal surfaces.