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.
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