Atomistic calculation of vacancy-formation free energies by reversible vacancy creation

M. DE KONING; S. RAMOS DE DEBIAGGI; A. M. MONTI

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

American Physical Society

Lugar: New York; Año: 2004 vol. 70 p. 54105 - 54115

0163-1829

We discuss technical aspects of the reversible vacancy-creation method for the computation of formation free energies as a function of temperature. The method is based on the introduction of a vacant lattice site into an otherwise perfect crystal by reversibly turning o® the interactions between an atom and its surroundings, while allowing for full volumetric relaxations. By measuring the work associated with this process, the formation free energy can be computed directly using short nonequilibrium MD simulations. The method is applied to determine the monovacancy formation free energy as a function of temperature for the Voter-Chen EAM model for Ni, and is found to be signi¯cantly less demanding than the standard thermodynamic integration. The method is not restricted to single vacancies and is applicable to compute the formation free energies of point-defect clusters, surfaces, as well as chemical potentials associated with di®erent atomic species in alloys.