${\it Ab \: initio}$ density-functional studies of 13-atom Cu and Ag clusters

TL;DR

This study uses ab initio molecular dynamics based on density-functional theory to identify low-symmetry bilayer structures as the likely ground states of 13-atom Cu and Ag clusters, differing from previously proposed configurations.

Contribution

It introduces a new class of low-symmetry bilayer structures as ground-state candidates for Cu13 and Ag13 clusters, validated through AIMD simulations and comparison with other DFT methods.

Findings

Low-symmetry bilayer structures are energetically favorable by 0.4-0.5 eV.

Structure results are consistent across different basis sets and DFT implementations.

The identified structures differ from earlier proposed buckled bi-planar configurations.

Abstract

The putative ground-state structures of 13-atom Cu and Ag clusters have been studied using ${\it ab \: initio}$ molecular-dynamics (AIMD) simulations based on the density-functional theory (DFT). An ensemble of low-energy configurations, collected along the AIMD trajectory and optimized to nearest local minimum-energy configurations, were studied. An analysis of the results indicates the existence of low-symmetric bilayer structures as strong candidates for the putative ground-state structure of Cu$_{13}$ and Ag$_{13}$ clusters. These bilayer structures are markedly different from a buckled bi-planar (BBP) configuration and energetically favorable, by about 0.4$-$0.5 eV, than the latter proposed earlier by others. Our study reveals that the structure of the resulting putative global-minimum configuration is essentially independent of the nature of basis functions (i.e., plane waves versus pseudoatomic orbitals) employed in the calculations, for a given exchange-correlation functional. The structural configurations obtained from plane-wave-based DFT calculations show a slightly tighter or dense first-shell of Cu and Ag atoms than those from local-basis functions. A comparison of our results with recent full-potential DFT simulations is presented.