Island morphology and adatom self-diffusion on Pt(111)

TL;DR

This study uses density functional theory to analyze step formation energies and adatom diffusion barriers on Pt(111), revealing insights into surface morphology and stress relaxation effects, with results aligning well with experimental data.

Contribution

It provides a detailed DFT analysis of step formation energies and diffusion barriers on Pt(111), highlighting the role of relaxation and comparing exchange-correlation approximations.

Findings

(111)-faceted step is energetically favored over (100)-faceted step

Diffusion barrier is approximately 0.33 eV, higher than experimental values

Relaxation significantly affects both step formation and diffusion barriers

Abstract

The results of a density-functional-theory study of the formation energies of (100)- and (111)-faceted steps on the Pt(111) surface, as well as of the barrier for diffusion of an adatom on the flat surface, are presented. The step formation energies are found to be in a ratio of 0.88 in favour of the (111)-faceted step, in excellent agreement with experiment; the equilibrium shape of islands should therefore clearly be non-hexagonal. The origin of the difference between the two steps is discussed in terms of the release of stress at the surface through relaxation. For the diffusion barrier, we also find relaxation to be important, leading to a 20% decrease of its energy. The value we obtain, 0.33 eV, however remains higher than available experimental data; possible reasons for this discrepancy are discussed. We find the ratio of step formation energies and the diffusion barrier to be the same whether using the local-density approximation or the generalized-gradient approximation for the exchange-and-correlation energy.