Overcoming the Time Limitation in Molecular Dynamics Simulation of Crystal Nucleation: A Persistent-Embryo Approach*

The nucleation of a crystalline phase in liquid is a typical rare event and is usually inaccessible within the limited timescales of conventional molecular dynamics (MD) simulations under experimental conditions. In this talk, we present a “persistent embryo” method to facilitate crystal nucleation in MD simulations, in which a small crystal embryo is inserted into the liquid, with spring forces applied to keep the embryo from melting. The springs are gradually weakened as the embryo grows and are completed removed when the nucleus size remains significantly smaller than the critical size. In this way, one can observe the spontaneous fluctuations of a critical nucleus in an unbiased environment, without any assumptions on the shape of the critical nucleus. We applied this method to simulate crystal nucleation under realistic experimental conditions and obtained results that compare favorably with experiments and other simulation methods. We will show this accelerated dynamic approach provides ample statistics for the critical sampling of the nucleation.