Reconstruction Mechanism of FCC Transition-Metal (001) Surfaces

TL;DR

This study uses density-functional theory to explore how (001) surfaces of FCC transition metals reconstruct, revealing that late 5d metals tend to form a quasi-hexagonal overlayer due to surface stress driven by relativistic effects.

Contribution

It provides a detailed computational analysis of the reconstruction mechanisms of FCC (001) transition-metal surfaces, highlighting the role of surface stress and relativistic effects.

Findings

Late 5d metals like Ir, Pt, Au undergo surface reconstruction.

Surface stress is the main driver of reconstruction in these metals.

Relativistic effects cause the stress difference between 4d and 5d metals.

Abstract

The reconstruction mechanism of (001) fcc transition metal surfaces is investigated using a full-potential all-electron electronic structure method within density-functional theory. Total-energy supercell calculations confirm the experimental finding that a close-packed quasi-hexagonal overlayer reconstruction is possible for the late 5$d$-metals Ir, Pt, and Au, while it is disfavoured in the isovalent 4$d$ metals (Rh, Pd, Ag). The reconstructive behaviour is driven by the tensile surface stress of the unreconstructed surfaces; the stress is significantly larger in the 5$d$ metals than in 4$d$ ones, and only in the former case it overcomes the substrate resistance to the required geometric rearrangement. It is shown that the surface stress for these systems is due to $d$ charge depletion from the surface layer, and that the cause of the 4th-to-5th row stress difference is the importance of relativistic effects in the 5$d$ series.