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LEED determination of the structures of Ni(111) and the p(2*2) overlayer of potassium on Ni(111)

The authors have used dynamical low-energy electron diffraction (LEED) to determine the structure of both the clean Ni(111) surface and the p(2*2) structure of potassium adsorbed on Ni(111). The result of the clean surface study indicates that the Ni(111) is essentially a truncation of the bulk crystal. The p(2*2) structure of potassium on this surface consists of the potassium atoms adsorbed on top of the Ni atoms with a slight reconstruction of the top-layer Ni atoms combined with vertical relaxations of the first and second layers of Ni. The potassium-nickel bond length is 2.82+or-0.04 AA corresponding to an effective potassium radius of about 1.57 AA. This result fits well in the bond length versus coordination number trend observed for other alkali metal overlayers.