Structural relaxation, dynamical arrest and aging in soft-sphere liquids

• Published in: arXiv.org
• Main Authors: Mendoza-Méndez, Patricia, Peredo-Ortiz, Ricardo, Edilio Lázaro Lázaro, Chávez-Paez, M, Pacheco-Vázquez, F, Medina-Noyola, M, Elizondo-Aguilera, L F
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 17.08.2022
• Subjects: Aging; Balancing; Crossovers; Glass; Glass transition temperature; Liquids; Physics - Soft Condensed Matter; Relaxation time; Windows (intervals)
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2208.08436

We investigate the structural relaxation of a soft-sphere liquid quenched isochorically (\(\phi=0.7\)) and instantaneously to different temperatures \(T_f\) above and below the glass transition. For this, we combine extensive Brownian dynamics simulations and theoretical calculations based on the non-equilibrium self-consistent generalized Langevin equation (NE-SCGLE) theory. The response of the liquid to a quench generally consists of a sub-linear increase of the \(\alpha\)-relaxation time with system's age. Approaching the ideal glass-transition temperature from above (\(T_f>T^a\)) sub-aging appears as a transient process describing a broad equilibration crossover for quenches to nearly arrested states. This allows us to empirically determine an equilibration timescale \(t^{eq}(T_f)\) that becomes increasingly longer as \(T_f\) approaches \(T^a\). For quenches inside the glass (\(T_f\leq T^a\)) the growth rate of the structural relaxation time becomes progressively larger as \(T_f\) decreases and, unlike the equilibration scenario, \(\tau_{\alpha}\) remains evolving within the whole observation time-window.These features are consistently found in theory and simulations with remarkable semi-quantitative agreement, and coincide with those revealed in the similar and complementary exercise [Phys. Rev. {\bf 96}, 022608 (2017)] that considered a sequence of quenches with fixed final temperature \(T_f=0\) but increasing \(\phi\) towards the hard-sphere dynamical arrest volume fraction \(\phi^a_{HS}=0.582\). The NE-SCGLE analysis, however, unveils various fundamental aspects of the glass transition, involving the abrupt passage from the ordinary equilibration scenario to the persistent aging effects that are characteristic of glass-forming liquids. The theory also explains that, within the time window of any experimental observation, this can only be observed as a continuous crossover.