Dynamic low-energy electron diffraction was used to determine the structure of the clean Ni(111) surface and the p(2 x 2) structure of potassium adsorbed onto Ni(111). The clean-surface study indicated that Ni(111) was, in effect, a truncation of the bulk crystal. The p(2 x 2) structure of potassium on this surface consisted 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 was 2.82Å corresponding to an effective potassium radius of about 1.57Å. This result fits well in the bond length versus coordination number trend observed for other alkali metal overlayers.

LEED Determination of the Structures of Ni(111) and the p(2 x 2) Overlayer of Potassium on Ni(111). P.Kaukasoina, M.Lindroos, R.D.Diehl, D.Fisher, S.Chandavarkar, I.R.Collins: Journal of Physics - Condensed Matter, 1993, 5[18], 2875-86