A LEED CRYSTALLOGRAPHIC ANALYSIS FOR THE C(2X2) SURFACE-STRUCTURE FORMED BY THE CHEMISORPTION OF PH3 ON THE RH(100) SURFACE

An analysis with low-energy electron diffraction (LEED) is reported for the c(2 x 2) structure obtained by the adsorption and dissociation of PH3 on the Rh(100) surface. Intensity-versus-energy curves measured for 12 independent beams were compared with those from multiple scattering calculations for overlayer structural models in which the metal atoms remain in their regular bulk positions. The best correspondence between the two sets of beam intensities occurs with P atoms chemisorbed in the "expected" 4-coordinate bonding sites, and with the nearest-neighbour P-Rh bond distance equal to 2.13 angstrom.