Freezing of a Lennard-Jones fluid: from nucleation to spinodal regime.
Using molecular dynamics, we investigate the crystal nucleation in a Lennard-Jones fluid as a function of the degree of supercooling. At moderate supercooling, a nucleation picture applies, while for deeper quenches, the phenomenon progressively acquires a spinodal character. We show that in the nucleation regime, the freezing is a two-step process. The formation of the critical nucleus is indeed preceded by the abrupt formation of a precritical crystallite from a density fluctuation in the fluid. In contrast, as the degree of supercooling is increased, crystallization proceeds in a more continuous and collective fashion and becomes more spatially diffuse, indicating that the liquid is unstable and crystallizes by a spinodal mechanism.
Trudu
Federica
F
ETH Zurich, Department of Chemistry and Applied Biosciences, c/o USI-Campus, via Giuseppe Buffi 13, CH-6900 Lugano, Switzerland.
Donadio
Davide
D
Parrinello
Michele
M