arXiv subjects

Ricardo Peredo-Ortiz

Publications and source records attributed to Ricardo Peredo-Ortiz.

3 recordsLinked to original sources

arXiv2026

Interference of dynamical arrest, thermodynamic instabilities and energy-scale competition in symmetric binary mixtures

While energy scale competition dictates equilibrium phase behavior, kinetic barriers often drive soft-matter mixtures into dynamically arrested states, rendering conventional phase diagrams incomplete. We extend the classification of binary systems into regions of thermodynamic instability to explore the interplay between phase separation and dynamical arrest. Strong cross-attractions kinetically suppress demixing, whereas competitive energy scales yield either condensation- or demixing-driven amorphous states. We show that this morphological crossover is parameterized by a structural order parameter, $χ$, providing a unified non-equilibrium framework that reconciles theoretical predictions with experimentally observed arrested mixtures.

cond-mat.soft↗

arXiv2023

Non-equilibrium Onsager-Machlup theory

This paper proposes a simple mathematical model of non-stationary and non-linear stochastic dynamics, which approximates a (globally) non-stationary and non-linear stochastic process by its locally (or \emph{"piecewise"}) stationary version. Profiting from the elegance and simplicity of both, the exact mathematical model referred to as the Ornstein-Uhlenbeck stochastic process (which is \emph{globally} stationary, Markov and Gaussian) and of the Lyapunov criterion associated with the stability of stationarity, we show that the proposed non-linear non-stationary model provides a natural extension of the Onsager-Machlup theory of equilibrium thermal fluctuations, to the realm of non-stationary, non-linear, and non-equilibrium processes. As an illustrative application, we then apply the extended non-equilibrium Onsager-Machlup theory, to the description of thermal fluctuations and irreversible relaxation processes in liquids, leading to the main exact equations employed to construct the \emph{non-equilibrium self-consistent generalized Langevin equation} (NE-SCGLE) theory of irreversible processes in liquids. This generic theory has demonstrated that the most intriguing and long-unsolved questions of the glass and the gel transitions are understood as a natural consequence of the second law of thermodynamics, enunciated in terms of the proposed piecewise stationary stochastic mathematical model.

cond-mat.stat-mech↗

arXiv2022

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

We investigate the structural relaxation of a soft-sphere liquid quenched isochorically ($ϕ=0.7$) 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 $α$-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, $τ_α$ 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 $ϕ$ towards the hard-sphere dynamical arrest volume fraction $ϕ^a_{HS}=0.582$. 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.

cond-mat.soft↗