The reversible vacancy-creation method for the estimation of formation free-energies as a function of temperature was considered. The method was based upon the introduction of a vacant lattice site, into an otherwise perfect crystal, by reversibly turning off the interactions between an atom and its surroundings; while allowing for full volumetric relaxation. By measuring the work which was associated with this process, the formation free-energy could be estimated directly by using short non-equilibrium molecular dynamics simulations. The method was used to determine the monovacancy formation free-energy as a function of temperature for the Voter-Chen embedded-atom model for Ni. It was found to be significantly less demanding than standard thermodynamic integration. The method was applicable to the estimation of the formation free-energies of point-defect clusters and surfaces.

Atomistic Calculation of Vacancy-Formation Free Energies by Reversible Vacancy Creation. M.de Koning, S.Ramos de Debiaggi, A.M.Monti: Physical Review B, 2004, 70[5], 054105 (10pp)