X-RAY-DIFFRACTION INVESTIGATION OF THE SULFUR INDUCED 4X1 RECONSTRUCTION OF NI(110)

The atomic structure of the Ni(110)4 x 1-S reconstruction has been det ermined on the basis of surface X-ray diffraction measurements. An ana lysis of the in-plane diffraction data shows that the model consists o f Ni rows along the [001] direction, two for every 4 x 1 unit cell, co rresponding to 0.5 ML Ni coverage. The S is chemisorbed in pseudo two- fold hollow sites both on the Ni rows and in the troughs between the r ows with a S coverage of 0.75 ML. Furthermore, rod-scans along fractio nal-order reflections reveal sub-surface relaxations. The results are in good agreement with recent STM and previous AES and radioactive tra cer studies.