Concentration profiles of low-index surfaces of PtNi alloys: Results of an improved thermodynamic approach

W. Hofer and L.Z. Mezey*

Institut für Allgemeine Physik, Technische Universität Wien, A-1040 Wien, Austria
*Institute of Physics, TU Budapest, H-1111 Budapest, Hungary

Mikrochim. Acta 125 (1997) 93-99

Earlier a general theory of solid surfaces was developed by one of us (MTCIP: Modern Thermodynamic Calculation of Interface Properties). A part of this theory describes the surface concentration profile for the thermodynamic equilibrium state by a system of non-linear equations. This system was solved in a first approximation for dilute mixtures and applied to several bimetallic alloys, with reliable results in several publications, even in the case of surface interactions with environmental (oxygen) atoms.
Recently a much more detailed second approximation (MTCIP-2A) has been developed, permitting - among other improvements - extension of the description to more concentrated alloys as well. Its description is under publication now, and is shortly outlined here, too.
Here we present calculated concentration profiles for the (100), (110) and (111) surfaces of PtNi (for T=1120K). These profiles are in good agreement with existing experimental values for all the surface orientations and all the bulk concentrations; mostly the values are within the experimental error. These results are discussed and compared with other theoretical calculations, which - as it is known - can be quite problematic for PtNi.

Corresponding author: W. Hofer (hofer< encoded email address >).