Strain effects on ensemble populations in AuPd∕Pd(100) surface alloys

The effects of applied strain on the arrangement of atoms in AuPd∕Pd(100) surface alloys are studied using Monte Carlo simulations and cluster expansion Hamiltonians. The strain effects are found to be significant, with heteronuclear (Au-Pd) interactions more strongly enhanced by biaxial compression than homonuclear (Pd-Pd) ones. In particular, compressive strain causes an increase in the population of Pd monomers and second nearest-neighbor pairs of Pd monomers, both of which have been identified previously as important ensembles for various catalytic reactions. We also discuss the origin of these effects using density functional theory calculations of the surface electronic structure of strained AuPd∕Pd(100). Our findings may suggest an additional means of employing strain to tune the catalytic properties of surface alloys.