THE IMPROVED MTCIP-1A (MODERN THERMODYNAMIC CALCULATION OF INTERFACE PROPERTIES - 1ST APPROXIMATION) AND ITS APPLICATION TO THE (PT)NI SURFACES

The MTCIP (modern thermodynamic calculation of interface properties) theory states the general conditions of the thermodynamic equilibrium state (TES) for any kind of interface, 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 successfully 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 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 last qualitatively, and in most cases even quantitatively, although the PtNi surfaces were the most problematic for theoretical calculations.