Calculation of elastic strain and electronic effects on surface segregation

Abstract

We present an electronic theory for calculating the heat of impurity segregation at metal surfaces by considering both the electronic contribution to the surface energy and the size-mismatch energy. The attractive part of the total energy is described by a multiband tight-binding Hartree Hamiltonian, and for the repulsive part Born-Mayer-type interatomic repulsions are assumed, which may depend on charge transfer. With simplifying assumptions about the density of states and the charge transfer, the heat of segregation and the equilibrium geometry can be obtained from an expression which depends only on the bulk cohesive energy, the bulk modulus, and the atomic size of the alloy components. Using this theory, we calculate the heat of segregation of Rh, Cu, and Au impurities on different Pt single-crystal surfaces and make a comparison with existing experimental data.