First principles study of adsorbed Cu_n (n=1-4) microclusters on MgO(100): structural and electronic properties

TL;DR

This study uses density functional theory to analyze the structural and electronic properties of small copper clusters on MgO(100), revealing preferred adsorption sites, diffusion barriers, and how cluster size affects stability and cohesion.

Contribution

It provides detailed first-principles insights into the adsorption geometries, energies, and electronic properties of Cu_n clusters on MgO(100), highlighting size-dependent stability trends.

Findings

Single Cu adatom prefers on-top oxygen site

Diffusion barrier around 0.45 eV at hollow site

Cluster stability increases with size, with Cu-Cu cohesion dominating

Abstract

We present a density functional study of the structural and electronic properties of small Cu_n (n=1,4) aggregates on defect-free MgO(100). The calculations employ a slab geometry with periodic boundary conditions, supercells with up to 76 atoms, and include full relaxation of the surface layer and of all adsorbed atoms. The preferred adsorption site for a single Cu adatom is on top of an oxygen atom. The adsorption energy and Cu-O distance are E_S-A = 0.99 eV and d_S-A = 2.04 Angstroems using the Perdew-Wang gradient corrected exchange correlation functional. The saddle point for surface diffusion is at the "hollow" site, with a diffusion barrier of around 0.45 eV. For the adsorbed copper dimer, two geometries, one parallel and one perpendicular to the surface, are very close in energy. For the adsorbed Cu_3, a linear configuration is preferred to the triangular geometry. As for the tetramer, the most stable adsorbed geometry for Cu_4 is a rhombus. The adsorption energy per Cu atom decreases with increasing the size of the cluster, while the Cu-Cu cohesive energy increases, rapidly becoming more important than the adsorption energy.