LEED structure analysis of A √3 × √3 -30° overlayer of iodine on Ag{111}

New preparation methods, new LEED intensity data and a new analysis on the classic much studied adsorbed system Ag{111}√3 × √3-30°-I suggest that this system can have several structural arrangements: in fact, we found a somewhat different structure than that found in 1973 by Forstmann, Berndt and Büttner. We were unable to produce a stable structure satisfactory for LEED analysis by the method used in the 1973 study. The earlier model with I in the three-fold symmetrical hollows with no Ag atom below does not fit our experiments satisfactorily, but models in which I atoms occupy both types of three-fold hollows fit better. © 1982.