Free Energies of Solid–Solid Alloy Interfaces with Interstitials

We present a method to calculate the free energies of coherent interfaces with interstitial atoms by using atomistic simulations. The method is applicable to single metals and multicomponent alloys and only requires a small number of simulations of systems of several thousand atoms. This method uses the Bennett acceptance ratio (modified to estimate diffusion potential) along with semigrand-canonical Monte Carlo simulations as well as a simple form of cavity-biased Monte Carlo to accelerate grand-canonical Monte Carlo in crystalline systems. As an example, we show the reduction in stacking fault free energy as a function of hydrogen concentration in nickel and a nickel alloy.