Phase transitions in adsorbed layers formed on crystals of square and rectangular surface lattice

This article gives a survey of phase transitions in adsorbed films on well defined surfaces of square and rectangular symmetry of the lattice. The dis cussion concentrates on the effects of periodic changes of the adsorbate-su bstrate potential on the structure and thermodynamic properties of adsorbed films. Different theoretical approaches are briefly reviewed, with an emph asis on those which explicitly take into account final corrugation of the s urface potential. Several aspects of statistical mechanical description of phase transitions in surface layers, such as order-disorder, melting, comme nsurate-incommensurate transitions in monolayer films as well as transition s connected with the formation of multilayer films (layering and wetting) a re presented. Theoretical discussion is followed by the presentation of num erous experimental and computer simulation studies for various systems. The n the properties of monolayer films of molecular adsorbates on different su bstrates of a square and rectangular symmetry is discussed. It is pointed o ut that computer simulation methods provide a very powerful tool which allo ws to probe the inner structure of such systems and provides direct informa tion concerning both orientational and positional ordering. (C) 2000 Elsevi er Science B.V. All rights reserved.