Abstract
We present a theoretical study of clusters from a few hundred to a few thousand of atoms, using Monte Carlo simulations and quenched molecular dynamics. This is performed within tight-binding many-body potentials, the tight-binding Ising model and the second moment approximation, which properly account for chemical and structural changes at transition-metal surfaces. The respective stabilities of the fcc, bcc, and icosahedral cluster shape are discussed in terms of competition or synergy between surface segregation and bulk ordering. Besides a finite-size effect on surface segregation, due to the limited quantity of matter, we show that chemical ordering can induce some geometrical frustrations and enhance the stability of “stoichiometric” clusters, the composition of which is strongly size dependent. Finally, it is found that chemical ordering leads to morphological transitions at equiconcentration.
- Received 20 November 2001
DOI:https://doi.org/10.1103/PhysRevB.66.045413
©2002 American Physical Society