PHASE-TRANSITIONS IN SURFACE SEGREGATION OF PTCNI1-C ALLOYS FROM TIGHT-BINDING ISING-MODEL CALCULATIONS

The tight-binding Ising model coupled with a mean-field approximation formulated as an area-preserving map is applied to surface segregation of PtcNi1-c alloys. It allows us to reproduce the striking experimental data available for the low-index faces and in particular the face-related segregation reversal observed when going from the (111) to the (110) face. Moreover, it predicts some spectacular phase transitions of the concentration profiles as a function of temperature and bulk concentration. © 1990 The American Physical Society.