Concentration profiles of low-index surfaces of PtCo alloys: application of an improved thermodynamic theory

• Published in: Surface science 1996-05, Vol.352, p.15-20
• Main Authors: Mezey, L.Z., Hofer, W.
• Format: Article
• Language: English
• Subjects: Alloys; Cobalt; Equilibrium thermodynamics; Low index single crystal surfaces; Platinum; Surface segregation; Surface thermodynamics
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(95)01082-3

Several years ago a general theory of solid surfaces was developed by one of us (MTCIP: modern thermodynamic calculation of interface properties). A part of it describes the surface concentration profile of the thermodynamic equilibrium state by a system of coupled, non-linear equations. This system was solved in a first approximation for dilute binary 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 (under publication now). It has been shown to give good agreement with experimental concentration profiles for the three low-index surfaces of PtNi for all the bulk concentrations investigated experimentally (for T ≈ 1120 K). Here the MTCIP-2A is shortly outlined and applied to obtain concentration profiles for Pt 25Co 75(110), Pt 25Co 75(111) and Pt 80Co 20(111) surfaces (for T = 1120 K). These results, too, are in agreement with recent LEED experiments for all the surface layers investigated. To our knowledge, these are the first calculated surface concentration profiles for PtCo.