Phase transitions in adsorbed layers formed on the (100) plane of face centered cubic crystals

The Monte Carlo simulation method is used to study the structure and phase transitions in adsorbed films formed on the (100) plane of the model face-c entered cubic crystals characterized by the different corrugation of the su rface potential. The systems consisting of the adsorbate atoms that tend to form the c(2 x 2) registered phase are studied. It is shown that the actua l structure of the dense monolayer films depends on the corrugation of the surface potential and on the density of the adsorbed layer and the temperat ure. The mechanism of melting transition in submonolayer, monolayer, and bi layer films is discussed. In particular, it is demonstrated that the submon olayer (incommensurate and registered) films retain monolayer character upo n melting, whereas melting of a dense (incommensurate) two-dimensional soli d is accompanied by the promotion of the second layer. The phase diagrams f or a series of systems are determined. It is shown that the location of the critical point for the first-layer condensation is affected considerably b y the surface corrugation. In the second layer formed on weakly corrugated surfaces and built on top of the dense incommensurate first layer, the effe cts due to the surface potential corrugation seem to be negligible. One obs erves the strong influence of the first-layer roughness (induced by the sur face potential corrugation) on the critical temperature of the second-layer condensation only in the strongly corrugated surfaces.