Surface diffusion in two‑dimensional clusters
Raniya R. Nafikova1, Nikita P. Kryuchkov1, Stanislav O. Yurchenko1; 1Soft Matter and Physics of Fluid Centre, Bauman Moscow State Technical University, Moscow, Russia.
Abstract
Diffusion is a key phenomenon governing structure formation and dynamics in soft matter systems. It has long been studied predominantly under bulk conditions. However, near phase boundaries, particle mobility can differ markedly from that in the interior. In this work, molecular dynamics simulations using the LAMMPS package were used to study surface diffusion of particles in two-dimensional monodisperse clusters for a set of generalized power-law Lennard-Jones (n–m) potentials with different ratios of repulsive to attractive stiffness: 12-6, 12-9, 12-5, 12-4, 12-3, 9-6, and 48-6.
Particle mobility was decomposed into radial and tangential components relative to the cluster center, with layer-resolved analysis (cluster sizes of 5, 6, 7, 10, 15, and 20 layers) across a temperature range of T = 0.3-0.7, with cluster identification via DBSCAN and periodic boundary conditions.
It was shown that diffusion coefficients decrease by 2-3 orders of magnitude when moving from the outer layers of the cluster to its core, while tangential mobility on average exceeds radial mobility, forming a pronounced diffusion anisotropy at the cluster edge. The degree of this anisotropy is related to the local packing density of particles, which is determined by the potential stiffness: stiffer potentials (48-6, 12-9) produce a higher and faster-saturating density near the cluster core compared to softer ones (12-3, 9-6).
The resulting dependence of surface diffusion anisotropy on potential shape provides a basis for future studies of how such clusters respond to external fields and for the targeted control of their structural dynamics.
Speaker
Raniya R. Nafikova
Soft Matter and Physics of Fluid Centre, BMSTU
Russia
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