Thermodynamics of vacancies in concentrated solid solutions: From dilute Ni-alloys to the Cantor system

TL;DR

This study investigates vacancy concentrations in concentrated (CoCrFeMn)Ni alloys using Monte Carlo simulations and thermodynamic modeling, revealing how chemical environment diversity influences vacancy formation energies and concentrations.

Contribution

It introduces a comprehensive thermodynamic model validated by Monte Carlo simulations for vacancy behavior across alloy compositions.

Findings

Vacancy formation energies show distribution dependent on alloy concentration.

Vacancy concentration can be accurately predicted by a Maxwell-Boltzmann weighted model.

Excellent agreement between thermodynamic predictions and Monte Carlo simulation results.

Abstract

The vacancy concentration at finite temperatures is studied for a series of (CoCrFeMn)$_{1-x_\mathrm{Ni}}$Ni$_{x_\mathrm{Ni}}$ alloys by grand-canonical Monte-Carlo (MC) simulations. The vacancy formation energies are calculated from a classical interatomic potential and exhibit a distribution due to the different chemical environments of the vacated sites. In dilute alloys, this distribution features multiple discrete peaks, while concentrated alloys exhibit an unimodal distribution as there are many different chemical environments of similar vacancy formation energy. MC simulations using a numerically efficient bond-counting model confirm that the vacancy concentration even in concentrated alloys may be calculated by the established Maxwell-Boltzmann equation weighted by the given distribution of formation energies. We calculate the variation of vacancy concentration as function of Ni content in the (CoCrFeMn)$_{x_\mathrm{Ni}}$Ni$_{1-x_\mathrm{Ni}}$ and prove the excellent agreement of the thermodynamic model and the results from the grand-canonical Monte-Carlo simulations.