Atomic structure of Tb(11 bar 20)

A low-energy electron-diffraction intensity analysis of a Tb(11 bar 20) surface finds that the atomic structure of this surface is different from bulk structure in two ways: The spacing between the first and the second layer, which have two inequivalent atoms in the unit mesh, is contracted by 3.3% (0.06 A), and the two inequivalent atoms in the first layer translate parallel to the surface by equal and opposite amounts of 0.21 A. Thus the change in registration of the composite surface layer preserves both the size and the symmetry of the unit mesh of parallel bulk layers. This kind of surface rearrangement is different from that reported by others for the (11 bar 20) surfaces of other rare-earth metals, such as Y, Gd, and Ho