arXiv subjects

Magdaleno Medina-Noyola

Publications and source records attributed to Magdaleno Medina-Noyola.

At least 19 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↗

arXiv2023

Non-Equilibrium View of the Amorphous Solidification of Liquids with Competing Interactions

The interplay between short-range attractions and long-range repulsions (SALR) characterizes the so called liquids with competing interactions, which are known to exhibit a variety of equilibrium and non-equilibrium phases. The theoretical description of the phenomenology associated to glassy or gel states in these systems has to take into account both, the presence of thermodynamic instabilities (such as those defining the spinodal line and the so called $λ$ line) and the limited capability to describe genuine non-equilibrium processes from first principles. Here we report the first application of the non-equilibrium self-consistent generalized Langevin equation theory, to the description of the dynamical arrest processes that occur in SALR systems after being instantaneously quenched into a state point in the regions of thermodynamic instability. The physical scenario predicted by this theory reveals an amazing interplay between the thermodynamically-driven instabilities, favoring equilibrium macro- and micro-phase separation, and the kinetic arrest mechanisms, favoring non-equilibrium amorphous solidification of the liquid into an unexpected variety of glass and gel states.

cond-mat.soft↗

arXiv2022

Phase separation and dynamical arrest of protein solutions dominated by short-range attractions

The interplay of phase separation and dynamical arrest can lead to the formation of gels and glasses, which is relevant for such diverse fields as hard and soft condensed matter physics, materials science, food engineering and pharmaceutical industry. Here, the non-equilibrium states as well as the interactions of globular proteins are analyzed. Lysozyme in brine is chosen as a model system with short-range attractions. The metastable gas-liquid binodal and the dynamical arrest line as well as the second virial coefficient $B_2$ have been determined for various solution conditions by cloud-point measurements, optical microscopy, centrifugation experiments and light scattering. If temperature is expressed in terms of $B_2$, the binodals obtained under various conditions fall onto a master curve, as suggested by the extended law of corresponding states. Arrest lines for different salt concentrations overlap within experimental errors, whereas they do not overlap if the temperature axis is replaced by $B_2$. This indicates that the binodals are not sensitive to the details of the potential, but can be described by one integral parameter, i.e. $B_2$, whereas the arrest line appears governed by its attractive part. The experimental findings are supported by numerical results of the non-equilibrium self-consistent generalized Langevin equation theory.

cond-mat.soft↗

arXiv2021

Waiting-time dependent non-equilibrium phase diagram of simple glass- and gel-forming liquids

Under many circumstances many soft and hard materials are present in a puzzling wealth of non-equilibrium amorphous states, whose properties are not stationary and depend on preparation. They are often summarized in unconventional "phase diagrams" that exhibit new "phases" and/or "transitions", in which the time, however, is an essential variable. This work proposes a solution to the problem of theoretically defining and predicting these non-equilibrium phases and their time-evolving phase diagrams, given the underlying molecular interactions. We demonstrate that these non-equilibrium phases and the corresponding non-stationary (i.e., aging) phase diagrams can indeed be defined and predicted using the kinetic perspective of a novel non-equilibrium statistical mechanical theory of irreversible processes. This is illustrated with the theoretical description of the transient process of dynamic arrest into non-equilibrium amorphous solid phases, of an instantaneously-quenched simple model fluid involving repulsive hard-sphere plus attractive square well pair interactions.

cond-mat.soft↗

arXiv2019

Analytical treatment of the structure and thermodynamics of the square-well fluid

The main goal of this work is to accurately reproduce the structural properties of attractive systems modelled by hard-sphere plus square-well (HS+SW) interaction potential. Based on the optimized random phase approximation (ORPA), the attractive part of the interaction potential is treated as a perturbation of the hard-sphere term. We are able to obtain an analytical expression for the structure factor $ S \left( k \right) $ which reproduces the low density limit. The microscopical structure of the fluid phase of several SW fluids is computed and compared with Monte Carlo (MC) simulation results showing that the structure factor is well reproduced in a wide range of wave vectors, in addition, the contact and discontinuity values of the radial distribution function are found to be in good agreement. Additionally, we compute the pressure equation of state and perform a quantitative analysis comparing with simulation results found that in a large set of densities and temperatures our approach outperform its linear form. Furthermore, we show that the theoretical approach developed in this study works very well for many thermodynamic states leading us a versatile and confident tool to systematic compute the structure and thermodynamics of SW fluids.

cond-mat.soft↗

arXiv2019

Arrested dynamics of the dipolar hard-sphere model

We report the combined results of molecular dynamics simulations and theoretical calculations concerning various dynamical arrest transitions in a model system representing a dipolar fluid, namely, N (softcore) rigid spheres interacting through a truncated dipole-dipole potential. By exploring different regimes of concentration and temperature, we find three distinct scenarios for the slowing down of the dynamics of the translational and orientational degrees of freedom: At low ({$η$} = 0.2) and intermediate ($η$ = 0.4) volume fractions, both dynamics are strongly coupled and become simultaneously arrested upon cooling. At high concentrations ({$η$} $\lt$ 0.6), the translational dynamics shows the features of an ordinary glass transition, either by compressing or cooling down the system, but with the orientations remaining ergodic, thus indicating the existence of partially arrested states. In this density regime, but at lower temperatures, the relaxation of the orientational dynamics also freezes. The physical scenario provided by the simulations is discussed and compared against results obtained with the self-consistent generalized Langevin equation theory, and both provide a consistent description of the dynamical arrest transitions in the system. Our results are summarized in an arrested states diagram which qualitatively organizes the simulation data and provides a generic picture of the glass transitions of a dipolar fluid.

cond-mat.soft↗

arXiv2018

Glassy dynamics in asymmetric binary mixtures of hard-spheres

The binary hard-sphere mixture is one of the simplest representations of a many-body system with competing time and length scales. This model is relevant to fundamentally understand both the structural and dynamical properties of materials, such as metallic melts, colloids, polymers and bio-based composites. It also allows us to study how different scales influence the physical behavior of a multicomponent glass-forming liquid; a question that still awaits a unified description. In this contribution, we report on distinct dynamical arrest transitions in highly asymmetric binary colloidal mixtures, namely, a single glass of big particles, in which the small species remains ergodic, and a double glass with the simultaneous arrest of both components. When the mixture approaches any glass transition, the relaxation of the collective dynamics of both species becomes coupled. In the single glass domain, spatial modulations occur due to the structure of the large spheres, a feature not observed in the two-glass domain. The relaxation of the \emph{self} dynamics of small and large particles, in contrast, become decoupled at the boundaries of both transitions; the large species always displays dynamical arrest, whereas the small ones appear arrested only in the double glass. Thus, in order to obtain a complete picture of the distinct glassy states, one needs to take into account the dynamics of both species.

cond-mat.soft↗

arXiv2018

Non-equilibrium Kinetics of the Transformation of Liquids into Physical Gels

A major stumbling block for statistical physics and materials science has been the lack of a uni- versal principle that allows us to understand and predict elementary structural, morphological, and dynamical properties of non-equilibrium amorphous states of matter. The recently-developed non- equilibrium self-consistent generalized Langevin equation (NE-SCGLE) theory, however, has been shown to provide a fundamental tool for the understanding of the most essential features of the transformation of liquids into amorphous solids, such as their aging kinetics or their dependence on the protocol of fabrication. In this work we focus on the predicted kinetics of one of the main fingerprints of the formation of gels by arrested spinodal decomposition of suddenly and deeply quenched simple liquids, namely, the arrest of structural parameters associated with the morpho- logical evolution from the initially uniform fluid, to the dynamically arrested sponge-like amorphous material. The comparison of the theoretical predictions (based on a simple specific model system), with simulation and experimental data measured on similar but more complex materials, suggests the universality of the predicted scenario.

cond-mat.soft↗

arXiv2017

Self-consistent generalized Langevin equation theory of the dynamics of multicomponent atomic liquids

A fundamental challenge of the theory of liquids is to understand the similarities and differences in the macroscopic dynamics of both colloidal and atomic liquids, which originate in the (Newtonian or Brownian) nature of the microscopic motion of their constituents. Starting from the recently-discovered long-time dynamic equivalence between a colloidal and an atomic liquid that share the same interparticle pair potential, in this work we develop a self-consistent generalized Langevin equation (SCGLE) theory for the dynamics of equilibrium multicomponent atomic liquids, applicable as an approximate but quantitative theory describing the long-time diffusive dynamical properties of simple equilibrium atomic liquids. When complemented with a Gaussian-like approximation, this theory is also able to provide a reasonable representation of the passage from ballistic to diffusive behavior. We illustrate the applicability of the resulting theory with three particular examples, namely, a monodisperse and a polydisperse monocomponent hard-sphere liquid, and a highly size-asymmetric binary hard-sphere mixture. To assess the quantitative accuracy of our results, we perform event-driven molecular dynamics simulations, which corroborate the general features of the theoretical predictions.

cond-mat.soft↗

arXiv2015

Non-equilibrium Theory of Arrested Spinodal Decomposition

The Non-equilibrium Self-consistent Generalized Langevin Equation theory of irreversible relax- ation [Phys. Rev. E (2010) 82, 061503; ibid. 061504] is applied to the description of the non- equilibrium processes involved in the spinodal decomposition of suddenly and deeply quenched simple liquids. For model liquids with hard-sphere plus attractive (Yukawa or square well) pair potential, the theory predicts that the spinodal curve, besides being the threshold of the thermo- dynamic stability of homogeneous states, is also the borderline between the regions of ergodic and non-ergodic homogeneous states. It also predicts that the high-density liquid-glass transition line, whose high-temperature limit corresponds to the well-known hard-sphere glass transition, at lower temperature intersects the spinodal curve and continues inside the spinodal region as a glass-glass transition line. Within the region bounded from below by this low-temperature glass-glass tran- sition and from above by the spinodal dynamic arrest line we can recognize two distinct domains with qualitatively different temperature dependence of various physical properties. We interpret these two domains as corresponding to full gas-liquid phase separation conditions and to the for- mation of physical gels by arrested spinodal decomposition. The resulting theoretical scenario is consistent with the corresponding experimental observations in a specific colloidal model system.

cond-mat.soft↗

arXiv2013

Molecular-Brownian Correspondence in the Hard-sphere Dynamic Universality Class

We perform systematic simulation experiments on model systems with soft-sphere repulsive interactions to test the predicted dynamic equivalence between soft-sphere liquids with similar static structure. For this we compare the simulated dynamics (mean squared displacement, intermediate scattering function, α-relaxation time, etc.) of different soft-sphere systems, between them and with the hard-sphere liquid. We then show that the referred dynamic equivalence does not depend on the (Newtonian or Brownian) nature of the microscopic laws of motion of the constituent particles, and hence, applies independently to colloidal and to atomic simple liquids. In addition, we verify another more recently-proposed dynamic equivalence, this time between the long-time dynamics of a Brownian fluid and its corresponding atomic liquid (i.e., the atomic system with the same interaction potential).

cond-mat.soft↗

arXiv2012

Equilibration and aging of dense soft-sphere glass-forming liquids

The recently-developed non-equilibrium extension of the self-consistent generalized Langevin equation theory of irreversible relaxation [Phys. Rev. E (2010) 82, 061503; ibid. 061504] is applied to the description of the irreversible process of equilibration and aging of a glass-forming soft-sphere liquid that follows a sudden temperature quench, within the constraint that the local mean particle density remains uniform and constant. For these particular conditions, this theory describes the non-equilibrium evolution of the static structure factor S(k;t) and of the dynamic properties, such as the self-intermediate scattering function F_S(k,τ;t), where tau is the correlation delay time and t is the evolution or waiting time after the quench. Specific predictions are presented, for the deepest quench (to zero temperature). The predicted evolution of the alpha-relaxation time τ_α(t) as a function of t allows us to define the equilibration time t^{eq}, as the time after which τ_αhas attained its equilibrium value τ_α^{eq}. It is predicted that both, t^{eq}(ϕ) and τ_α^{eq}, diverge as ϕ\to ϕ^{(a)}, where ϕ^{(a)} is the hard-sphere dynamic-arrest volume fraction ϕ^{(a)}\ (\approx 0.582), thus suggesting that the measurement of equilibrium properties at and above ϕ^{(a)} is experimentally impossible.

cond-mat.soft↗

arXiv2012

Generalized Langevin Equation for Tracer Diffusion in Atomic Liquids

We derive the time-evolution equation that describes the Brownian motion of labeled individual tracer particles in a simple model atomic liquid (i.e., a system of $N$ particles whose motion is governed by Newton's second law, and interacting through spherically symmetric pairwise potentials). We base our derivation on the generalized Langevin equation formalism, and find that the resulting time evolution equation is formally identical to the generalized Langevin equation that describes the Brownian motion of individual tracer particles in a colloidal suspension in the absence of hydrodynamic interactions. This formal dynamic equivalence implies the long-time indistinguishability of some dynamic properties of both systems, such as their mean squared displacement, upon a well-defined time scaling. This prediction is tested here by comparing the results of molecular and Brownian dynamics simulations performed on the hard sphere system.

cond-mat.soft↗

arXiv2012

Overdamped van Hove function of atomic liquids

Using the generalized Langevin equation formalism and the process of contraction of the description we derive a general memory function equation for the thermal fluctuations of the local density of a simple atomic liquid. From the analysis of the long-time limit of this equation, a striking equivalence is suggested between the long-time dynamics of the atomic liquid and the dynamics of the corresponding \emph{Brownian} liquid. This dynamic equivalence is confirmed here by comparing molecular and Brownian dynamics simulations of the self-intermediate scattering function and the long-time self-diffusion coefficient for the hard-sphere liquid.

cond-mat.soft↗

arXiv2012

Dynamic equivalence between atomic and colloidal liquids

We show that the kinetic-theoretical self-diffusion coefficient of an atomic fluid plays the same role as the short-time self-diffusion coefficient D_S in a colloidal liquid, in the sense that the dynamic properties of the former, at times much longer than the mean free time, and properly scaled with D_S, will indistinguishable from those of a colloidal liquid with the same interaction potential. One important consequence of such dynamic equivalence is that the ratio D_L/ D_S of the long-time to the short-time self-diffusion coefficients must then be the same for both, an atomic and a colloidal system characterized by the same inter-particle interactions. This naturally extends to atomic fluids a well-known dynamic criterion for freezing of colloidal liquids[Phys. Rev. Lett. 70, 1557 (1993)]. We corroborate these predictions by comparing molecular and Brownian dynamics simulations on (soft- and hard-sphere) model systems, representative of what we may refer to as the "hard-sphere" dynamic universality class.

cond-mat.soft↗

arXiv2011

Density-Temperature-Softness Scaling of the Dynamics of Glass-forming Soft-sphere Liquids

The principle of dynamic equivalence between soft-sphere and hard-sphere fluids [Phys. Rev. E \textbf{68}, 011405 (2003)] is employed to describe the interplay of the effects of varying the density n, the temperature T, and the softness (characterized by a softness parameter ν^{-1}) on the dynamics of glass-forming soft-sphere liquids in terms of simple scaling rules. The main prediction is that the dynamic parameters of these systems, such as the α-relaxation time and the long-time self-diffusion coefficient, depend on n, T, and ν only through the reduced density n^\ast \equiv nσ^{3}_{HS}(T, ν),where the effective hard-sphere diameter σ_{HS}(T, ν) is determined, for example, by the Andersen-Weeks-Chandler condition for soft-sphere-hard-sphere structural equivalence. A number of scaling properties observed in recent simulations involving glass-forming fluids with repulsive short range interactions are found to be a direct manifestation of this general dynamic equivalence principle. The self-consistent generalized Langevin equation (SCGLE) theory of colloid dynamics is shown to accurately capture these scaling rules

cond-mat.soft↗

arXiv2011

Equilibration of Concentrated Hard Sphere Fluids

We report a systematic molecular dynamics study of the isochoric equilibration of hard-sphere fluids in their metastable regime close to the glass transition. The thermalization process starts with the system prepared in a non-equilibrium state with the desired final volume fraction ϕ but with a prescribed non-equilibrium static structure factor S_0(k; ϕ). The evolution of the α- relaxation time τα (k) and long-time self-diffusion coefficient DL as a function of the evolution time tw is then monitored for an array of volume fractions. For a given waiting time the plot of τα (k; ϕ, tw) as a function of ϕ exhibits two regimes corresponding to samples that have fully equilibrated within this waiting time (ϕ \leq ϕ(c) (tw)), and to samples for which equilibration is not yet complete (ϕ \geq ϕ(c) (tw)). The crossover volume fraction ϕ(c) (tw) increases with tw but seems to saturate to a value ϕ(a) \equiv ϕ(c) (tw \rightarrow \infty) \approx 0.582. We also find that the waiting time t^(eq)_w(ϕ) required to equilibrate a system grows faster than the corresponding equilibrium relaxation time, t^(eq)(ϕ) \approx 0.27 \times [τα (k; ϕ)]^1.43, and that both characteristic times increase strongly as ϕ approaches ϕ^(a), thus suggesting that the measurement of equilibrium properties at and above ϕ(a) is experimentally impossible.

cond-mat.soft↗