Location of an O atom in the Pd(110)c(2×4)-O structure. An EELS study

The Pd(110)c(2×4)-O surface has been investigated mainly by high-resolution electron energy loss spectroscopy. Two losses have been observed at 62 and 68 meV for the c(2×4) surface, which is consistent with the structure model involving substrate reconstruction into the (1×2) missing-row structure where the O atoms are located in the three-coordinated sites of the (111) microfacets to form zig-zag chains along the [110] Pd rows. The losses are attributed to the hindered motions of an O atom perpendicular and parallel to the (111) microfacet, respectively. A calculation of the vibrational energies of a Pd3O cluster based on Wilsonʹs GF matrix technique suggests that the first interlayer spacing is expanded compared to that of the bulk.