Local structure of the Ag(100) surface reacting with molecular iodine: Experimental and theoretical study

Abstract

Room-temperature adsorption of molecular iodine on Ag͑100͒ has been studied by scanning tunneling microscopy ͑STM͒, low-energy electron diffraction, Auger electron spectroscopy with factor analysis, and density-functional theory ͑DFT͒. We have found that at chemisorption stage iodine forms only one ordered phase c͑2 ϫ 2͒ described by a simple ͑ ͱ 2 ϫ ͱ 2͒R45°unit cell. DFT calculations have shown that energetically most favorable configuration of this square lattice corresponds to iodine atoms adsorbed in fourfold hollow sites on the silver surface. Further iodine dosing leads to the growth of two-dimensional islands of silver iodide. The STM images of the silver-iodide surface demonstrate a clear visible superstructure with a periodicity ͑2 ͱ 2 ϫ 12 ͱ 2͒R45°superimposed with a quasihexagonal atomic modulation. As a result of the DFT simulations of the AgI islands, a new sandwichlike phase was obtained, which appears to be different from all known bulk structures of silver iodide. In the direction perpendicular to the sample face, it consists of two coupled silver planes located between two iodine planes. According to calculations, the "sandwich," as a whole, is situated on top of the c͑2 ϫ 2͒ iodine monolayer. The validity of the proposed structural model is confirmed by the excellent correspondence between experimental and simulated STM images.

Resonance Raman intensity analysisof the excited‐state photochemical dynamicsof dimethyl 1,3‐dithiole‐2‐thione‐4,5‐dicarboxylate in the A‐band absorption

“…Both samples showed similar morphological characters of the nanoislands, as shown in the SEM images. The formation of these nanoislands are analogous to previous reports of silver iodide formed on silver surface with very low iodine concentrations 17–23. Increasing the iodine content (e.g., elongating the solution processing time and the iodine concentration) results in the increase of both the size and density of the nanoislands on the silver surface (see Supporting Information, Figure S1).…”

Silver Surface Iodination for Enhancing the Conductivity of Conductive Composites

“…[ 34 ] On the other hand, earlier scanning tunneling microscopy (STM) and ab initio studies also show that at a very low iodination level, the chemisorbed iodine affects the structural and electronic properties of the metal surface and induces lateral displacement of silver atoms. [ 35 ] The adsorption layer is weakly associated to the silver metal surface due to the crystalline mismatch, [ 18 ] and they can go through structural changes and cover less areas when subjected to heat. [ 36 ] When silver goes through a solution based iodination, those iodinated regions occupy active sites such as the terraces and steps of the silver surface more selectively, and experience a subsequent ripening process, [ 17 , 18 , 28 , 37 ] leaving the remaining part a clean silver surface due to an electrochemical process, [ 17 , 18 ] although the dynamic process still needs further investigation.…”

“…The formation of these nanoislands are analogous to previous reports of silver iodide formed on silver surface with very low iodine concentrations. [17][18][19][20][21][22][23] Increasing the iodine content (e.g., elongating the solution processing time and the iodine concentration) results in the increase of both the size and density of the nanoislands on the silver surface (see Supporting Information, Figure S1). …”

Electron spectroscopies and inelastic processes in nanoclusters and solids: Theory and experiment

“…A large number of ab initio calculations have been performed to predict the Auger energies of atomic and molecular spectra and the results obtained are generally in fairly good agreement with the experimental data; see, e.g., [42,49,[132][133][134][135][136][137][138][139][140][141][142]. Very different is the situation for solids and extended systems, where the theoretical and computational treatment of electronic excitations, particularly neutral ones, still presents many difficulties.…”