Structural Determination of the Unreconstructed and the Reconstructed (110) Surfaces of Iridium

An Ir(110)-(1 multiplied by 1) surface has been prepared by adsorbing 1/4 monolayer of oxygen at 850 K on a clean, reconstructed (1 multiplied by 2) surface. Good agreement was achieved between theoretical and experimental intensity-voltage (I-V) spectra for a surface model in which the oxygen is randomly and uniformly distributed over the cyrstal surface, and the (1 multiplied by 1) structure is the same as for a clean unreconstructed (1 multiplied by 1) surface with a topmost interlayer spacing of 1. 26+360. 05 A. Three different models have been tested for the reconstructed Ir(110)-(1 multiplied by 2) surface, namely, the missing-row model, the paired rows model, and the buckled surface model. Based on the comparison between experimental data (consisting of ten half-order beams and eight integral-order beams) and the theoretical calculations, the mising-row model with a topmost interlayer spacing of 1. 22+360. 07 A is the most satisfactory model tested.