The adiabatic switching molecular dynamics method was used to determine bulk and vacancy-formation Gibbs free energies as a function of temperature at zero pressure. The bulk free energy was determined by using isochoric isothermal switching procedures, in which a system that consisted of 500 atoms which interacted via a semi-empirical tight-binding potential was converted into a system of 500 independent and identical 3-dimensional harmonic oscillators. The equilibrium volumes of these simulations were deduced from equilibrium isobaric isothermal molecular dynamics simulations. The frequency of the oscillators was chosen so as to be of the order of a principal Cu phonon frequency. It was found that the resultant bulk free energy and entropy were in excellent agreement with experimental data. The vacancy-formation Gibbs free energy was estimated by using isobaric isothermal switching procedures in which the interactions of a single Cu atom were switched off. In spite of the limited accuracy of the interatomic potential, and error propagation through the small energy differences which were involved, the estimated formation enthalpies and entropies (1.27eV and 2.9k) agreed remarkably well with experimental data (1.28eV and 2.5k).

Adiabatic Switching Applied to Realistic Crystalline Solids: Vacancy-Formation Free Energy in Copper. M.De Koning, A.Antonelli: Physical Review B, 1997, 55[2], 735-44