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Slow dynamics of a confined supercooled binary mixture: direct space analysis.
P Gallo1, R Pellarin, M Rovere
1Dipartimento di Fisica, Università Roma Tre, Instituto Nazionale per la Fisica della Materia, Unità di Ricerca Roma Tre, INFM, Democritos National Simulation Center, Via della Vasca Navale 84, Italy. gallop@fis.uniroma3.it
Summary
Supercooling a binary mixture in a soft sphere matrix reveals smaller particles avoid interfaces, decreasing mobility. This confinement alters dynamics and narrows the validity of mode coupling theory.
Area of Science:
- Condensed matter physics
- Materials science
- Computational chemistry
Background:
- Understanding supercooled liquids is crucial for materials science.
- Lennard-Jones binary mixtures and soft sphere models are used to study liquid dynamics.
- Confinement effects can significantly alter the dynamical properties of liquids.
Purpose of the Study:
- To investigate the dynamical properties of a Lennard-Jones binary mixture confined within a soft sphere matrix during supercooling.
- To compare the system's behavior with predictions from mode coupling theory (MCT).
- To analyze the impact of confinement on particle mobility and dynamic crossover temperatures.
Main Methods:
- Molecular dynamics (MD) simulations were employed to study the system in direct space.
- The simulations focused on a Lennard-Jones binary mixture embedded in an off-lattice soft sphere matrix.
- Temperature was systematically lowered to observe supercooling effects.
Main Results:
- Smaller particles were observed to avoid soft sphere interfaces upon cooling, leading to decreased mobility.
- The system's dynamic behavior was found to be consistent with mode coupling theory predictions.
- A reduction in the mode coupling crossover temperature was observed compared to bulk systems.
- The range of validity for mode coupling theory was found to shrink under confinement.
Conclusions:
- Confinement in a soft sphere matrix significantly impacts the dynamics of binary mixtures.
- The avoidance of interfaces by smaller particles and enhanced hopping processes contribute to deviations from bulk behavior.
- Mode coupling theory's applicability is limited in confined systems, especially at higher temperatures than the crossover.