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**The improved MTCIP-1A (Modern Thermodynamic Calculation of Interface Properties - First Approximation) and its application to the (Pt)Ni surfaces**

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L.Z. Mezey^{*} and W. Hofer

*
Institut für Allgemeine Physik,
Technische Universität Wien, A-1040 Wien, Austria*

^{*}Institute of Physics, TU Budapest, H-1111 Budapest, Hungary
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*Surf. Interface Anal. 19 (1992) 618-622*

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).