Crystal Nucleation Kinetics in Supercooled Germanium: MD Simulations versus Experimental Data.

Abstract

The validity of the classical nucleation theory (CNT), the most important tool to describe and predict nucleation kinetics in supercooled liquids, has been at stake for almost a century. Here, we carried out comprehensive molecular dynamics simulations of the nucleation kinetics of a fast quenched supercooled germanium using the Stillinger-Weber potential at six temperatures, covering a supercooling range of T/Tm = 0.70-0.86, where Tm is the equilibrium melting temperature. We used the seeding method to determine the number of particles in the critical crystal nuclei at each supercooling, which yielded n* = 150-1300 atoms. The transport coefficient at the liquid/nucleus interface and the melting point were also obtained from the simulations. Using the parameters resulting directly from the simulations, the CNT embraces the experimental nucleation rates, J(T), with the following fitted (average) values of the nucleus/liquid interfacial free energy: γ = 0.244 and 0.201 J/m2, for the experimental and calculated values of thermodynamic driving force, Δμ(T), respectively, which are close to the value obtained from n*(T). Without using any fit parameter, the calculated nucleation rates for the experimental and calculated values of Δμ(T) embrace the experimental J(T) curve. Therefore, this finding favors the validity of the CNT.