Local collective dynamics at equilibrium BCC crystal-melt interfaces

TL;DR

This study uses molecular dynamics to analyze the collective dynamics at equilibrium BCC Fe crystal-melt interfaces, revealing anisotropic speed-up in dynamics and validating a theoretical model for interface kinetics.

Contribution

It provides new insights into the anisotropic collective dynamics at BCC crystal-melt interfaces and validates the time-dependent Ginzburg-Landau theory for kinetic coefficients.

Findings

Anisotropic speed-up of collective dynamics at interfaces

Significant difference from liquid-vapor interface behavior

Excellent agreement with TDGL theory for kinetic coefficients

Abstract

We present a classical molecular-dynamics study of the collective dynamical properties of the coexisting liquid phase at equilibrium body-centered cubic (BCC) Fe crystal-melt interfaces. For the three interfacial orientations (100), (110), and (111), the collective dynamics are characterized through the calculation of the intermediate scattering functions, dynamical structure factors and density relaxation times in a sequential local region of interest. An anisotropic speed up of the collective dynamics in all three BCC crystal-melt interfacial orientations is observed. This trend differs significantly different from the previously observed slowing down of the local collective dynamics at the liquid-vapor interface [Acta Mater 2020;198:281]. Examining the interfacial density relaxation times, we revisit the validity of the recently developed time-dependent Ginzburg-Landau (TDGL) theory for the solidification crystal-melt interface kinetic coefficients, resulting in excellent agreement with both the magnitude and the kinetic anisotropy of the CMI kinetic coefficients measured from the non-equilibrium MD simulations