Theory of surface segregation: self-consistent determination of the concentration profile

摘要

Ab-initio studies of surface segregation in alloys are based on the Ising-type Hamil-tonian, whose parameters are the effective cluster interactions (ECI). The ECIs for alloy surfaces can be determined by various methods, e.g., by the Connolly-Williams inversion scheme~1-3. or by the generalized perturbation method (GPM)~4. The GPM relies on the force theorem~5, according to which only the band terms is mapped onto the Ising Hamiltonian in the bulk case. The case of macroscopically inhomogeneous system, like disordered surfaces is more complex. The ECIs can be determined on two levels of sophistication.