Calculated Pre-exponential Factors and Energetics for Adatom Hopping on Terraces and Steps of Cu(100) and Cu(110)

TL;DR

This study calculates vibrational properties and energetics for copper adatom hopping on Cu(100) and Cu(110) surfaces, providing detailed diffusion barriers, entropy contributions, and prefactors using atomistic modeling methods.

Contribution

It offers new computational insights into vibrational effects and energetics of adatom diffusion on copper surfaces, aligning well with experimental data.

Findings

Diffusion energy barriers agree with experiments and prior theories.

Vibrational entropy significantly influences free energy changes.

Prefactors are approximately 10^-3 cm^2/s, stable across temperatures.

Abstract

We have calculated the vibrational dynamics and thermodynamics for Cu adatom hopping on terraces and near step edges on Cu(100) and Cu(110), using the embedded atom method for the interatomic potential. The local vibrational densities of states were calculated using real space Green's function formalism and the thermodynamical functions were evaluated in the harmonic approximation. The calculated diffusion energy barriers for six specific local environments on Cu(100) agree well with experimental and previous theoretical results. Contribution of vibrational entropy to the change in the free energy of the system as the adatom moves from the equilibrium configuration (hollow site) to the saddle point, is found to be as much as 55meV (144 meV) at 300K (600K). The prefactors for all 13 cases are found to be of the order of 10-3 cm2/s, almost independent of temperature, and the respective activation energy barriers.