Computer simulation study of surface wave dynamics at the crystal--melt interface

TL;DR

This study uses computer simulations to analyze surface wave dynamics at the crystal-melt interface across different systems, revealing distinct relaxation time scales and the influence of microscopic details on interface behavior.

Contribution

It provides a comparative analysis of surface wave relaxation in hard-spheres, Lennard Jones, and water models, highlighting the role of microscopic dynamics and orientational degrees of freedom.

Findings

Surface wave relaxation involves slow (recrystallization/melting) and fast (perturbation) processes.

Relaxation becomes slower with increasing wavelength and is unaffected by microscopic details.

Water's interface relaxation is slower due to orientational degrees of freedom.

Abstract

We study, by means of computer simulations, the crystal-melt interface of three different systems: hard-spheres, Lennard Jones and the TIP4P/2005 water model. In particular, we focus on the dynamics of surface waves. We observe that the processes involved in the relaxation of surface waves are characterized by distinct time scales: a slow one related to the continuous recrystallization and melting, that is governed by capillary forces; and a fast one which we suggest to be due to a combination of processes that quickly cause small perturbations to the shape of the interface (like e. g. Rayleigh waves, subdiffusion, or attachment/detachment of particles to/from the crystal). The relaxation of surface waves becomes dominated by the slow process as the wavelength increases. Moreover, we see that the slow relaxation is not influenced by the details of the microscopic dynamics. In a time scale characteristic for the diffusion of the liquid phase, the relaxation dynamics of the crystal-melt interface of water is around one order of magnitude slower than that of Lennard Jones or hard spheres, which we ascribe to the presence of orientational degrees of freedom in the water molecule. Finally, we estimate the rate of crystal growth from our analysis of the capillary wave dynamics and compare it with previous simulation studies and with experiments for the case of water.