Surface segregation trends in transition metal alloys.

In this work, we revisit the problem of predicting the surface segregation trends in binary transition metal alloys from the knowledge of the basic features of the pure component d-band electronic structure within tight- binding approximation. In contrast to previous trend studies, the present one includes, within the fourth-moment approximation (FMA) of the tight-binding scheme, both the difference in the average band energies (diagonal disorder) and the difference in the band widths (off-diagonal disorder) of the two components. We show that treating on the same footing these two effects is essential for a correct prediction of surface segregation. The presented study, giving a natural link between the electronic structure and mixing/segregation properties, is particularly interesting and useful in the context of the possibility of building efficient new energy models based on FMA for use in large (time) scale atomistic simulations. [ABSTRACT FROM AUTHOR]