A Theoretical Study of the Adsorbate-Induced Reconstruction of the (110) Surface of Nickel and a Molecular Analog

Recent experimental data have shown that the (110) surface of nickel with adsorbed oxygen reconstructs to give a missing-row structure, but with adsorbed hydrogen, a Peierls-like pairing of these rows is found. With CO, the surface does not reconstructat all. We show that although the row/row pair potential, calculated via the tight-binding method, is negative for the clean nickel surface, it becomes positive, indicating repulsion between the metal atoms, on adsorption of oxygen in accord with experiment.The crossing point in the potential moves toward the left of the transition-metal series on adsorption of oxygen, the extent of the movement being controlled by the size of the metal-oxygen interaction. A similar effect is calculated to occur on Ni(100). Similar results are predicted for CO on nickel, a result not in accord with experiment, but the pair potential is significantly reduced if the CO groups are arranged in the zigzag manner found experimentally. For hydrogen on nickel, it is shown how the pairing distortion is also sensitive to adsorption, being energetically favorable for hydrogen coverages greater than 1. In order to tie these results together, a simple molecular analogue is presented.