DEVELOPMENT OF FINNIS-SINCLAIR TYPE POTENTIALS FOR PB, PB-BI, AND PB-NI SYSTEMS - APPLICATION TO SURFACE SEGREGATION

Empirical many-body potentials of a Finnis-Sinclair-type have been con structed for the Pb, Pb-Bi and Pb-Ni systems using both experimental d ata and physical quantities derived from ab initio linear muffin-tin o rbitals calculations. Monte Carlo simulations using these potentials h ave been employed to compute the solubility limits of Pb-Bi and Pb-Ni alloys, as well as the segregation profiles at the (111) surface of Pb 95Bi05. The profiles have been found to be oscillatory, with a prefere ntial segregation of Pi occurring at the first surface atom layer, and a slight depletion of Bi in the second layer, in fair agreement with the results of the ab initio linear muffin-tin orbitals calculations. The calculations on Pb-Ni show that within the solubility limit of Ni in Pb, Ni does not segregate to the Pb(111) outermost surface layer,al though weak segregation to the second layer is found. (C) 1998 Acta Me tallurgica Inc.