Surface structure and stress in Fe monolayers on W(110)

We present a surface x-ray structure analysis of Fe on W(110) deposited at room temperature in the coverage range up to 1.7 ML, in combination with in situ stress measurements. The maximum compressive stress is observed at about 0.7 ML, and coincides with the maximum first-layer Fe occupancy. Further island coalescence is inhibited. The onset of tensile stress at higher coverage is related with the growth of the second pseudomorphic Fe layer. At 1.2 ML only fractions of 0.70 +/- 0.10 and 0.10 +/- 0.10 ML of Fe, in the first and second layers, respectively, are located in pseudomorphic sites. At 1.7 ML three pseudomorphic Fe layers (with fractional ML occupancies of 0.80+/-0.10, 0.60 +/- 0.10, and 0.20+/-0.10) have to be taken into account to fit the x-ray intensities indicating the growth of three-dimensional islands. The layer occupancies are consistent with scanning tunneling microscopy images. The Fe-W and Fe-Fe interlayer distances are compressed by up to 13% relative to the bulk distances, in good agreement with previous theoretical predictions and experiments.