Simulation of lattice-strain-driven bcc-->fcc phase transitions in Pd thin films.

Abstract

Monte Carlo simulations are used to examine the structural properties of Pd thin films deposited on a rigid bcc(110) substrate. The embedded-atom-method potential has been employed to represent the Pd-Pd and Pd-substrate interactions. The structure of the thin films was examined for coverages ranging from 0.25 to 1.75 monolayers (ML). We observe a competition between the relief of interfacial strain, favoring pseudomorphic growth, and the relief of intralayer strain within the Pd adlayer, which favors an incommensurate structure. We find that Pd grows pseudomorphically up to 1 bcc-equivalent ML of adatoms; however, a commensurate-${\mathrm{Pd}}_{\mathrm{bcc}}$(110) to incommensurate-${\mathrm{Pd}}_{\mathrm{fcc}}$(111) phase transition is predicted to occur within the first monolayer for coverages between 1.00 and 1.25 bcc ML.