Hydrogen on W(110): an adsorption structure revisited

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