2024/11/21 by Omar Hussein, Yang Li, Hussein, Omar +3
Computer Science · Physics and Astronomy · #Computational Physics and Python Applications #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Quantum many-body systems #Soft Condensed Matter (cond-mat.soft)
paper · pdf · doi:10.48550/arxiv.2411.14610
openalex publication_date 2024/11/21 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
It has long been believed that the atomic dynamics in disordered structures, such as undercooled liquids and pre-melted interfaces, are characterized by collective atomic rearrangements in the form of quasi-one-dimensional chains of atomic displacements (strings) and their closed forms (rings). Here, we show by molecular dynamics (MD) simulations that strings involving more than a few atoms do not form by a single collective event. Instead, they represent trajectories of propagating local density perturbations, which we call densitons. The atoms on this trajectory are almost indistinguishable from their environments except for the moving head of the string (densiton). A densiton migrates by either single-atom jumps or a concerted rearrangement of 2-3 atoms. The simulations reveal a remarkable similarity between the strings in disordered and crystalline structures, in which the densitons localize into point defects. This work calls for a significant reinterpretation of the string concept and instead proposes a densiton model of the atomic dynamics.