Grain boundaries with relatively low energies could be superheated above the melting temperature and eventually melt by heterogeneous nucleation of liquid droplets. A thermodynamic model for this process was proposed which was based upon the sharp-interface approximation with a disjoining potential. A distinct feature of the model was its ability to predict the shape and size of the critical nucleus by using a variational approach. The model reduces to the classical nucleation theory in the limit of large nuclei but was more general and remained valid for small nuclei. Contrary to the classical nucleation theory, the model predicts the existence of a critical temperature of superheating and offers a simple formula for its calculation. The model was tested against molecular dynamic simulations in which liquid nuclei at a superheated boundary were obtained by an adiabatic trapping procedure. The simulation results demonstrated a reassuring consistency with the model.

Liquid Nucleation at Superheated Grain Boundaries. T.Frolov, Y.Mishin: Physical Review Letters, 2011, 106[15], 155702