Eur. Phys. J. Spec. Top.
https://doi.org/10.1140/epjs/s11734-026-02151-y

Regular Article

Angle-resolved collective dynamics of the interfacial liquid at an FCC crystal–melt interface

¹ School of Physics and Electronic Science, East China Normal University, 200241, Shanghai, China
² General Education College, Chongqing Polytechnic University of Electronic Technology, 401331, Chongqing, China

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Received: 29 November 2025
Accepted: 19 January 2026
Published online: 29 January 2026

Abstract

The collective dynamics of liquids near crystal–melt interfaces (CMIs) provide the microscopic input needed to predict anisotropic interface kinetics, yet their dependence on in-plane direction and wavelength remains poorly understood. Here we perform large-scale molecular-dynamics simulations of a Lennard–Jones FCC(100) crystal coexisting with its melt and apply a local formulation of the intermediate scattering function to map the relaxation times $\tau (q,\theta ,z)$ of the interfacial liquid. We focus on two characteristic wave-vector magnitudes corresponding to the principal and next-nearest reciprocal lattice vectors, $|\overrightarrow{K}|$ and $|\overrightarrow{G}|$, and systematically vary the in-plane angle $\theta$ and distance z from the interface. For both $|\overrightarrow{K}|$ and $|\overrightarrow{G}|$, we find strong spatial modulation of $\tau (q,\theta ,z)$ within a few atomic layers of the CMI, together with a pronounced in-plane anisotropy that peaks along the diagonal direction $\theta =\pi /4$. While high-symmetry directions ($\theta =0$ and $\pi /2$) exhibit interfacial acceleration of collective relaxation relative to the bulk liquid, the $\theta =\pi /4$ direction shows a dramatic slowdown, especially for $|\overrightarrow{G}|$, where the relaxation time can exceed the bulk value by nearly a factor of two and displays transient solid-like locking. These results reveal a rich and strongly anisotropic dynamical landscape in the interfacial liquid and provide the angle- and wavelength-resolved relaxation times required to incorporate directional collective dynamics into Ginzburg–Landau-type kinetic theories of crystal growth.