Eur. Phys. J. D 64, 37-44 (2011)
https://doi.org/10.1140/epjd/e2011-20129-9

Regular Article

Influence of the environment on equilibrium properties of Au-Pd clusters

¹ Physique des Solides Irradiés et des Nanostructures, CP234, Faculté des Sciences, Université Libre de Bruxelles, Bd. Du Triomphe, 1050 Bruxelles, Belgium
² Division of Molecular and Materials Simulation, Key Lab for Nanomaterials, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029, P.R. China
³ Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko Chaussée 72, 1784 Sofia, Bulgaria

^a e-mail: mhou@ulb.ac.be

Received: 26 February 2011
Received in final form: 8 April 2011
Published online: 27 July 2011

Abstract

The question of the influence of the environment on the structure and thermodynamic state of a bimetallic cluster is examined, using Metropolis Monte Carlo methods. An embedded atom model is used to estimate metal energies. The environment is modeled at a generic level as a rigid matrix which atoms interact with the atoms of an embedded Au-Pd cuboctahedral cluster via a Lennard Jones (LJ) potential. The high sensitivity of the cluster properties on its environment is demonstrated by scaling the LJ potential. It is found that the strength of the interfacial interactions completely determines surface segregation. Full segregation with either Au or Pd at the surface favors the occurrence of stable alloy phases in the cluster core while the subsurface layer acts as a buffer accommodating both the induced surface segregation and the inner composition constrained by phase stability. Cluster surface disorder induced by an amorphous matrix limits interface segregation and phase stability in the cluster core, even when the interfacial interaction strength is weak. The contrast between the epitaxial and amorphous matrix cases over a wide range of interface energies suggests the importance in the thermodynamic properties of the cluster core of the interfacial atomic arrangement in the matrix.