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 s urface structure supports a surface oxide model, as first postulated b y Orent and Bader. The detailed model which gives the best corresponde nce with experimental intensity data has a PdO(001) overlayer stacked on to the Pd(100) surface such that rumpling is induced in both the ox ide and topmost Pd(100) layers. The structure can be seen as represent ing a compromise between the drive toward an ideally flat PdO(001) sur face and the need to optimize total bonding at the surface. Pd atoms i n the topmost Pd(100) layer appear to displace laterally to minimize c orrugations 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 pre dicted value of 1.76 Angstrom based on the structure of bulk PdO.