EQUILIBRIUM AND NONEQUILIBRIUM PROPERTIES OF SOME TWO-DIMENSIONAL SYSTEMS (PHASE DIAGRAM, SOLITONS, VICINAL)

In this thesis, some equilibrium and nonequilibrium properties of two-dimensional lattice-gas models and surfaces are explored. In the first part of this work, the equilibrium properties of the two-dimensional anisotropic next-nearest-neighbour Ising (ANNNI) model are studied, including a derivation of an interfacial adsorption or wetting transition in this system and its properties. In the second part the kinetics of domain growth in this model is studied using Monte Carlo computer simulation methods. The effect of the wetting transition on the domain growth is investigated. As well, a phenomenological theory of domain growth for this model is developed. Also, both the equilibrium and nonequilibrium properties of this and similar models are studied using field theoretic methods and the properties of nonlinear differential equations. In the third part of this thesis the properties of ordered defects, in particular steps and kinks, are studied on metal and semiconductor surfaces. A new class of structural phase transitions is proposed, and a semimicroscopic theory for these transitions is developed. An extended classification scheme concerning the properties of phase transitions is presented for kinked surfaces. As well, the scattering and pair correlation functions are calculated for kinked surfaces. Also, a unified discussion of the equilibrium properties of surfaces and crystal shapes is given.