TENSER LEED ANALYSIS OF THE PD(100)-(ROOT-5X-ROOT-5)R27-DEGREES-O SURFACE-STRUCTURE

A tenser LEED analysis of the Pd(100)-(root 5 x root 5)R27 degrees-O surface structure supports a surface oxide model, as first postulated by Orent and Bader. The detailed model which gives the best correspondence with experimental intensity data has a PdO(001) overlayer stacked on to the Pd(100) surface such that rumpling is induced in both the oxide and topmost Pd(100) layers. The structure can be seen as representing a compromise between the drive toward an ideally flat PdO(001) surface and the need to optimize total bonding at the surface. Pd atoms in the topmost Pd(100) layer appear to displace laterally to minimize corrugations in the top metal layers. The total corrugations in the PdO overlayer and the first Pd(100) layer are indicated to be about 0.26 and 0.51 Angstrom, respectively. The average O-Pd bond length for two-coordinate O on the Pd surface (1.73 Angstrom) remains dose to the predicted value of 1.76 Angstrom based on the structure of bulk PdO.