RELIABILITY OF DETAILED LEED STRUCTURAL-ANALYSES - PT(111) AND PT(111)-P(2X2)-O

As surface structures are being examined in more detail than ever before, the reliability of structural details becomes an important issue. To discuss necessary components of a high quality, reliable dynamical LEED studies, detailed dynamical LEED analyses of the clean Pt(111) and the Pt(111)-p(2x2)-O structures have been carried out utilizing different computer programs and search methods applied to a common see of experimental LEED I-V data. We have investigated the effects of various non-structural parameters, in particular those involved in the construction of the phase shifts, on the resulting structures of the clean Pt(111) and the Pt(111)-p(2x2)-O surfaces. The use of relativistic Pt phase shifts is found to be important in order to determine the adsorption structure accurately. For clean Pt(111), we find the top interlayer spacing is noticeably expanded by 0.025+/-0.01 Angstrom with a low R(p)-factor value of 0.15. For the Pt(111)-p(2x2)-O system we find an R(p)-factor of 0.18. O atoms in the p(2x2)-O overlayer are found to adsorb in fcc-hollow sites and induce buckling in both the first and second metal layers. In addition, there is an expansion of the first metal-metal interlayer spacing and a small contraction of the second.