Adhesion of metal on metal. The Pt on Co case

Abstract

The adhesion of Pt overlayers in pseudomorphic epitaxy on hcp Co(0 0 0 1) and fcc Co(1 0 0) was investigated with first-principles calculations. This was compared to the adhesion of the Pt surface layers on Pt(1 1 1) and Pt(1 0 0). We show that adhesion can be analyzed by taking into account the interplay between the chemical and structural properties at the interface. The free Pt planes with the bulk Pt-Pt distance are submitted to tensile stress which can be relaxed by 6.6% and 9.1% contraction for the (1 1 1) and (1 0 0) symmetries respectively. This results in equilibrium interatomic distances which are not far from that of the Co substrate. Consequently the stress energy in a pseudomorphic Pt monolayer on a Co substrate is lower than the stress energy of pure Pt(1 1 1) or Pt(1 0 0) surfaces. However, this is at the expense of the Pt chemical reactivity towards the Co substrate. This is in agreement with the general dependence between chemical reactivity and stress of a metal surface. © 2001 Elsevier Science B.V. All rights reserved.