Breakdown of Stokes-Einstein relation in the supercooled liquid state of phase change materials

Abstract

The application of amorphous chalcogenide alloys as data-storage media relies on their ability to undergo an extremely fast (10-100 ns) crystallisation once heated at sufficiently high temperature. However, the peculiar features that make these materials so attractive for memory devices still lack a comprehensive microscopic understanding. By means of large scale molecular dynamics simulations, we demonstrate that the supercooled liquid of the prototypical compound GeTe shows a very high atomic mobility (D \sim 10^(-6) cm2/s) down to temperatures close to the glass transition temperatures. This behaviour leads to a breakdown of the Stokes-Einstein relation between the self- diffusion coefficient and the viscosity in the supercooled liquid. The results suggest that the fragility of the supercooled liquid is the key to understand the fast crystallisation process in this class of materials.

6 pages, 4 figures

References in corpus (3)

• Canonical sampling through velocity-rescaling
• Coexistence of tetrahedral and octahedral-like sites in amorphous phase change materials
• A neural network interatomic potential for the phase change material GeTe

Cited by in corpus (8)

• Crystal Nucleation in Liquids: Open Questions and Future Challenges in Molecular Dynamics Simulations
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• Relaxation and physical aging in network glasses: a review
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• Breakdown of the Stokes-Einstein Relation Above the Melting Temperature in a Liquid Phase-Change Material
• Metadynamics sampling in atomic environment space for collecting training data for machine learning potentials
• Characterization of the non-Arrhenius behavior of supercooled liquids by modeling non-additive stochastic systems
• Viscosity, breakdown of Stokes-Einstein relation and dynamical heterogeneity in supercooled liquid Ge${}_2$Sb${}_2$Te${}_5$ from simulations with a neural network potential