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 w ere collected normal to the (100) surface and 45 degrees off-normal al ong the [011] direction at room temperature. A close analysis of the a utoregressive linear-prediction-based Fourier transform indicates that the P atoms adsorb in the high-coordination fourfold hollow sites. Cu rved-wave multiple-scattering calculations confirmed the fourfold holl ow 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 o f the Fe surface. Self-consistent-field X alpha scattered-wave calcula tions were performed for the c(2 x 2)P/Fe(100) and the c(2 x 2)S/Fe(10 0) systems. These independent results are in excellent agreement with this P/Fe structure and the S/Fe structure previously published, confi rming the ARPEFS determination that the Fe-1-Fe-2 interlayer spacing i s contracted from the bulk value for S/Fe but not for P/Fe. Finally, t his structure is compared to structures from the literature of atomic nitrogen, atomic oxygen, and sulfur adsorbed on the Fe(100) surface.