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

The surface structures of face-centered-cubic Pd(210) and body-centered-cub ic 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 on ly 3%, followed by an expansion of both the second and third interlayer dis tances not seen at other comparable (210) surfaces. Relaxations parallel to the surface and to the mirror plane have been found to be below the detect ion limit for Pd(210). The Mo(211) surface, on the other hand, showed signi ficant shifting of surface atoms in the two topmost layers towards position s 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.