The MTCIP (modern thermodynamic calculation of interface properties) theory states the general conditions of the thermodynamic equilibrium state (TES) for any kind of interfaces, any number of components and interface sublayers. In the MTCIP-1A (first approximation) for a binary dilute solid mixture the monolayer surface composition is calculated in the TES (allowing for a chemisorbed or segregated overlayer as well). This approach has been used succesfully so far for bimetallic alloys and as well for the segregation of non-metallic solutes on metal surfaces, and is further developed here. This new version is used for the problematic PtNi surfaces, both low-index and polycrystalline. All the parameters needed to follow the calculations are given. In all cases, the theory agrees with the experiments at least qualitatively, and in most cases even quantitatively, although the PtNi surfaces were the most problematic for theoretical calculations.
Corresponding author: W. Hofer (hofer).