ALLOY SURFACES AND SURFACE ALLOYS - FROM EQUILIBRIUM TO KINETICS

We study the relation between the surface segregation at thermodynamical equilibrium in an alloy A(c)B1-c and the kinetics of dissolution of A/B or B/A. This is possible within a new kinetic model based on the electronic structure: the kinetic tight-binding Ising model. In particular, the existence of a local equilibrium between the surface and the first underlayer is stressed. Some illustrations are given in the particular case of two systems, one presenting a tendency to bulk phase separation and surface layering transitions (Cu-Ag) and the other a tendency to bulk ordering and surface concentration profile transitions (Pt-Ni). The notion of ''surface alloy'' is defined in the latter case.