Multilayer relaxation of Pd(210) and Mo(211)

The surface structures of face-centered-cubic Pd(210) and body-centered-cubic Mo(211) have been determined by low energy electron diffraction (LEED). We find substantial relaxations (with respect to the bulk layer separation) of the interlayer distances normal to the surface both for Pd(210) and Mo(211). The Mo(211) surface shows alternating contractions and dilatations of layer separations starting with a 16% contraction of the distance between first and second layers. For the Pd(210) surface, however, this value is only 3%, followed by an expansion of both the second and third interlayer distances not seen at other comparable (210) surfaces. Relaxations parallel to the surface and to the mirror plane have been found to be below the detection limit for Pd(210). The Mo(211) surface, on the other hand, showed significant shifting of surface atoms in the two topmost layers towards positions with higher local symmetry. Pendry R-factors between 0.209 and 0.205 have been obtained for the best fit geometries. (C) 1999 Elsevier Science B.V. All rights reserved.