A kinetic criterion for Stokes–Einstein relation breakdown based on effective collisional geometry

doi:10.1088/1674-1056/ae32ff

Abstract We propose a kinetic framework for interpreting the Stokes-Einstein (SE) relation breakdown in supercooled liquids by introducing an effective collision diameter, $d_{\mathrm{eff}}$, derived from transport data. Numerical simulations of a model CuZr alloy reveal that $d_{\mathrm{eff}}$ increases upon cooling but saturates near the first peak of the radial distribution function just before SE breakdown. This saturation defines a geometric upper bound for the collisional cross-section beyond which further slowdown is governed by cooperative, heterogeneous motion rather than local collisional transport. Our analysis yields a compact criterion for SE breakdown in a mean-field perspective and provides physically interpretable inputs for future data-driven models of glassy dynamics.

Keywords: metallic glass-forming liquids transport decoupling kinetic-geometric criterion

Received: 09 October 2025
Revised: 01 December 2025
Accepted manuscript online: 04 January 2026

PACS:	64.70.pe	(Metallic glasses)
	67.10.Jn	(Transport properties and hydrodynamics)
	05.20.Dd	(Kinetic theory)

Fund: This work was supported by the National Natural Science Foundation of China (Grant Nos. 12474184, 52031016, and 11804027).

Corresponding Authors: Zhen-Wei Wu
E-mail: zwwu@bnu.edu.cn

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Zhen-Wei Wu(武振伟) A kinetic criterion for Stokes–Einstein relation breakdown based on effective collisional geometry 2026 Chin. Phys. B 35 056402

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[1]	Universal basis underlying temperature, pressure and size induced dynamical evolution in metallic glass-forming liquids H P Zhang(张华平), B B Fan(范蓓蓓), J Q Wu(吴佳琦), and M Z Li(李茂枝). Chin. Phys. B, 2024, 33(1): 016101.

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A kinetic criterion for Stokes–Einstein relation breakdown based on effective collisional geometry

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