Phase transformations of the H/W(110) and H/Mo(110) surfaces

Abstract

We present results of combined theoretical and experimental studies of the surface phases produced by hydrogen adsorption on tungsten (110) and molybdenum (110) planes. We have formulated a theoretical model which has the following ingredients: (1) a possible adsorbate-induced lateral shift reconstruction of the substrate surface; (2) two-body and three-body interactions among hydrogen atoms; and (3) a coupling of the overlayer ordering to the substrate reconstruction. This model gives good agreement with the observed phase diagram for H/W(110) which shows a (2×1) phase at low coverages and a (2×2) phase, as well as substrate reconstruction, at high coverages. In the case of H/Mo(110), for which no reconstruction is observed, the lack of a (2×1) phase suggests the presence of a strong three-body interaction among the adatoms.