SELF-CONSISTENT ORDERING ENERGIES AND SEGREGATION PROFILES AT BINARY-ALLOY SURFACES

We discuss the application of the direct configurational averaging method to the calculation of the thermodynamic properties of alloy surfaces. We analyze critically a number of approaches previously proposed to determine the parameters in different Ising models. We investigate the physical meaning of various interaction energies occurring in those models and compare our technique to phenomenological approaches. The formalism is applied in electronically self-consistent mean-field calculations of the segregation profile at the surface of Ni-Cu and Rh-Ti alloys at temperatures above the bulk disordering temperature.