At one‐third of a monolayer coverage, sulfur forms an ordered (&sqrt;3×&sqrt;3)R30° superstructure on the Ir (111) surface. A comparison between dynamic calculations of the intensity–voltage profiles of diffracted beams for different assumed surface geometries and measured low‐energy electron diffraction beam profiles demonstrates that the sulfur adatoms occupy one of the two inequivalent types of threefold hollow sites. In particular, the sulfur resides in the threefold sites directly above a vacancy in the second substrate layer with an interlayer spacing of 1.65 A˚ corresponding to an Ir–S bond length of 2.28 A˚.
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