Calculation of the Nucleation Barrier and Interfacial Free Energy of New-Phase Nuclei by the Thermodynamic Integration Method Using Molecular Dynamics Simulation Data

An approach to determining the nucleation barrier and interfacial free energy (surface tension) based on molecular dynamics simulations of structural transformations, in particular, the formation of new phase nuclei, is reported. The approach is based on the thermodynamic integration method, wherein key elements are trajectories characterizing the potential energy change, which are obtained from independent numerical experiments. An important feature of the approach is its applicability to both equilibrium and nonequilibrium systems, as well as the possibility of determining the above thermodynamic characteristics for small new-phase nuclei, with a significant curvature of the surface. For example, we present the temperature dependencies of the surface tension of water droplet nuclei for water vapor nucleation and of the nucleation barrier to crystal nucleation in two model glassy systems, which are computed within the framework of the proposed approach. The calculated values of the surface tension coefficient of water droplet nuclei are compared with the available experimental data.