HYDROGEN ON W(110) - AN ADSORPTION STRUCTURE REVISITED

We present a quantitative study of the atomic structure of the clean a nd H-covered W(110) surface employing an analysis of low-energy electr on diffraction (LEED) as well as density functional theory (DFT) calcu lations. Our results give no evidence of a noteworthy reconstruction o f the W(110) surface upon H-adsorption, and thus discard the widely ac cepted model of a H-induced lateral shift of the top layer based on ea rlier LEED data. Moreover, we offer a reinterpretation of the latter w hich goes along without such a surface reconstruction. In detail. we f ind good agreement between the LEED analysis and the DFT calculations on a small contraction of the first interlayer distance by about 3% fo r the clean surface, which is reduced to half this size at full H cove rage. Hydrogen itself is found to be adsorbed in quasi-threefold coord inated hollow sites at a higher of about 1.20 Angstrom above the first substrate layer. (C) 1997 Elsevier Science B.V.