LEED study of the potassium-induced reconstruction of Cu(110)

We have used low-energy electron diffraction (LEED) to determine the adsorption geometry of the ordered p(2 x 2) potassium overlayer on the (potassium-induced) (1 x 2) missing-row reconstruction of Cu(110) at 47 K. The K adsorption site in this ordered structure is substitutional, whereby the K atoms occupy half of the Cu sites which are vacated in the missing-row reconstruction. The distance between the K atom and its nearest neighbours (in the second Cu layer) is 3.24 plus/minus 0.05 A. We observed very little, if any, lateral displacement of the second-layer Cu atoms, but a significant buckling in the third layer. The effect of this buckling is to pull the rows of third-layer Cu atoms which are directly beneath the K rows toward the surface, thus increasing the effective coordination of the K atoms.