Structure determination of chemisorbed c(2x2)P/Fe(100) using angle-resolved photoemission extended fine structure and self-consistent-field X alpha scattered-wave calculations: Comparison with c(2x2)S/Fe(100)
Angle-resolved photoemission extended fine structure (ARPEFS) was used to determine the structure of c(2 x 2)P/Fe(100). Photoemission data were collected normal to the (100) surface and 45 degrees off-normal along the  direction at room temperature. A close analysis of the autoregressive linear-prediction-based Fourier transform indicates that the P atoms adsorb in the high-coordination fourfold hollow sites. Curved-wave multiple-scattering calculations confirmed the fourfold hollow adsorption site. The P atoms were determined to bond 1.02 Angstrom above the first layer of Fe atoms and the Fe-P-Fe bond angle is 140.6 degrees. Additionally, it was determined that there was no expansion of the Fe surface. Self-consistent-field X alpha scattered-wave calculations were performed for the c(2 x 2)P/Fe(100) and the c(2 x 2)S/Fe(100) systems. These independent results are in excellent agreement with this P/Fe structure and the S/Fe structure previously published, confirming the ARPEFS determination that the Fe-1-Fe-2 interlayer spacing is contracted from the bulk value for S/Fe but not for P/Fe. Finally, this structure is compared to structures from the literature of atomic nitrogen, atomic oxygen, and sulfur adsorbed on the Fe(100) surface.