The adsorption position of Hg on Ni(100): a transmission channeling study

The adsorption position of Hg on Ni(100) has been studied with transmission channeling. It is shown that for coverages up to 0.5 monolayer (ML), Hg adsorbs in the four-fold hollow site (FFHS) at a height of 2.25 ± 0.10 rA. This is at variance with an earlier report of adsorption in the bridge site. For a crystal temperature of 115 K and low coverage (θ_Hg t 0.18 ML), the two-dimensional vibration amplitude parallel to the surface, ρ_Hg, is 0.10 +- 0.03 rA, but at higher coverage, θ_Hg 0.45 ML, there is an apparent increase in the root-mean-square displacement of the Hg atoms from the FFHS. Possible origins of this increase are discussed.