Tensor LEED analysis for the electrodeposited Pt(111)-(3x3)-Ag,I surface structure

A crystallographic analysis is reported using low-energy electron diffracti on (LEED) in the tensor LEED approach for the electrodeposited coadsorption (3 x 3) structure with 4/9 monolayer (ML) of silver and 4/9 ML of iodine o n the Pt(1 1 1) surface. The structure approximates a two-layer slice of bu lk AgI cut parallel to its (1 1 1) plane and superimposed on the substrate with the Ag atoms in contact with the topmost Pt(1 1 1) layer, and the I at oms forming an overlayer on the Ag atoms. There are two types of Ag atoms i n the (3 x 3) unit mesh; one type bonds to a single Pt atom, while the othe r type bonds to three Pt atoms. The average Ag-Pt bond distances are close to 2.48 and 2.82 (A) over circle respectively for the one and three-coordin ate Ag atoms, but both types of Ag atoms bond to three I atoms with an aver age Ag-I distance of 2.67 (A) over circle. No significant corrugation is ob served for either the I layer or the Ag layer. (C) 2001 Elsevier Science B. V. All rights reserved.