Cu/Ag EAM Potential Optimized for Heteroepitaxial Diffusion from ab initio Data

TL;DR

This paper develops an optimized embedded-atom method potential for Cu on Ag(111) surfaces based on ab initio data, improving the accuracy of modeling diffusion and energetics of Cu adatoms and small clusters.

Contribution

The paper introduces a modified Cu-Ag EAM potential fitted to DFT data, accurately reproducing monomer and dimer energies and geometries for Cu on Ag(111).

Findings

The optimized potential matches DFT monomer and dimer energies and geometries.

It predicts diffusion barriers consistent with DFT for monomers.

The potential can be used for larger Cu island simulations on Ag(111).

Abstract

A binary embedded-atom method (EAM) potential is optimized for Cu on Ag(111) by fitting to ab initio data. The fitting database consists of DFT calculations of Cu monomers and dimers on Ag(111), specifically their relative energies, adatom heights, and dimer separations. We start from the Mishin Cu-Ag EAM potential and first modify the Cu-Ag pair potential to match the FCC/HCP site energy difference then include Cu-Cu pair potential optimization for the entire database. The optimized EAM potential reproduce DFT monomer and dimer relative energies and geometries correctly. In trimer calculations, the potential produces the DFT relative energy between FCC and HCP trimers, though a different ground state is predicted. We use the optimized potential to calculate diffusion barriers for Cu monomers, dimers, and trimers. The predicted monomer barrier is the same as DFT, while experimental barriers for monomers and dimers are both lower than predicted here. We attribute the difference with experiment to the overestimation of surface adsorption energies by DFT and a simple correction is presented. Our results show that the optimized Cu-Ag EAM can be applied in the study of larger Cu islands on Ag(111).