In previous years a new theory, modern thermodynamic calculation of interface properties(MTCIP), was developed. Its general equations on the thermodynamic equilibrium were solved in a first approximation (MTCIP-1A) and applied to several dilute binary alloy systems in good agreement with experimental results, even in the case of surface reactions with the environment. Here, first a more developed second approximation (MTCIP-2A) is shortly outlined, allowing, among other new results, for any number of interface sublayers, and being valid in the total compositional range of the bulk. Then, by some simplifications, a new segregational isotherm is developed from it. Using the two dilute limits as described by the MTCIP-2A, then even with a single surface composition (measured at any bulk composition and temperature) this segregational isotherm permits to obtain surface compositions over the total bulk compositional range. Results are shown for the low-index surfaces of PtNi at temperatures of about 1100 K, mostly in better agreement with experimental values than other present theories.
Corresponding author: W. Hofer (hofer).