Structutral Phase Transitions in the Chemisorbed Chlorine Layer on Ag(100)

Structural transformations under chlorine adsorption on the Ag(100) surface have been studied with scanning tunneling microscopy (STM) and within the density functional theory (DFT) calculations. The DFT method reveals that the preferable adsorption site of chlorine atoms is the fourfold hollow position. The STM technique is used to study the disorder-order structural phase transition occurring at a gradual increase in the chlorine coverage, which results in formation of the c(2 x 2) structure on the Ag(100) surface. It is found that the critical coverage of the ordering corresponds to approximate to 0.34-0.35 monolayer (ML). The chemisorbed chlorine monolayer is saturated at the coverage of 0.5 ML corresponding to the formation of the c(2 x 2) structure. Further chlorine absorption leads to nucleation and growth of AgCl islands near the edges of atomic steps.