Structure, mechanical and thermodynamic stability of vacancy clusters in Cu

TL;DR

This study uses atomistic simulations to analyze the atomic, mechanical, and thermodynamic stability of vacancy clusters in copper, revealing how strain affects their formation energy and stability at different temperatures.

Contribution

It provides new insights into the stability and behavior of vacancy clusters in copper under various strains and temperatures, including their most stable configurations and dissociation probabilities.

Findings

Vacancy clusters' formation energy decreases with uniaxial strain.

Under volumetric strain, formation energy first increases then decreases.

Most vacancy clusters are thermodynamically stable, but some tend to dissociate.

Abstract

The atomic structure, mechanical and thermodynamic stability of vacancy clusters in Cu are studied by atomistic simulations. The most stable atomic configuration of small vacancy clusters is determined. The mechanical stability of the vacancy clusters is examined by applying uniaxial and volumetric tensile strain to the system. The yield stress and yield strain of the system are significantly reduced comparing to the prefect lattice. The dependence of vacancy formation and binding energy as a function of strain is explored and can be understood from the liquid-drop model. We find that the formation energy of the vacancy clusters decreases monotonically as a function of the uniaxial strain, while the formation energy increases first then decreases under the volumetric tensile strain. The thermodynamic stability of the vacancy clusters is analyzed by calculating the Gibbs free binding energy and the total probability of dissociation of the vacancy clusters at 300 K and 900 K under uniaxial and volumetric strains. We find that although most of the vacancy clusters appear to be thermodynamically stable, some of the immediate sized clusters have high probability of dissociation into smaller clusters.