Stress induced nanostructure in a Pd monolayer on Ni(1 1 0): a first principles theoretical study

Abstract

The formation energy of an epitaxial Pd adlayer on Ni(1 1 0) was calculated as a function of the cell parameter in the [1 1 ̄ 0] row direction. The optimal Pd–Pd distance is found to be 2.72 A ̊ , and the epitaxial stress energy of the monolayer at the Ni bulk parameter is estimated to be 90 meV/atom. A periodic reconstruction ( Λ×1) with the creation of vacancies in the palladium layer is proposed to explain the experimental observations and to allow a partial relaxation of the stress. The stability of these structures as a function of the reconstruction period is studied by density functional theory plane wave calculations. The energy is minimum for structures with a typical length around 15 A ̊ . This particular stability is discussed as a competition between stress relaxation, bond breaking associated with a vacancy, and epitaxial misfit.