# Browsing by Subject "cond-mat.soft"

Now showing 1 - 20 of 31

###### Results Per Page

###### Sort Options

Item Open Access A local view on the role of friction and shape(EPJ Web of Conferences, 2017) Schröter, MatthiasLeibniz said "Naturam cognosci per analogiam": nature is understood by making analogies. This statement describes a seminal epistemological principle. But one has to be aware of its limitations: quantum mechanics for example at some point had to push Bohr's model of the atom aside to make progress. This article claims that the physics of granular packings has to move beyond the analogy of frictionless spheres, towards local models of contact formation.Item Open Access Assembly of hard spheres in a cylinder: a computational and experimental study(2017-03-10) Fu, Lin; Bian, Ce; Shields, C Wyatt; Cruz, Daniela F; López, Gabriel P; Charbonneau, PatrickHard spheres are an important benchmark of our understanding of natural and synthetic systems. In this work, colloidal experiments and Monte Carlo simulations examine the equilibrium and out-of-equilibrium assembly of hard spheres of diameter $\sigma$ within cylinders of diameter $\sigma\leq D\leq 2.82\sigma$. Although in such a system phase transitions formally do not exist, marked structural crossovers are observed. In simulations, we find that the resulting pressure-diameter structural diagram echoes the densest packing sequence obtained at infinite pressure in this range of $D$. We also observe that the out-of-equilibrium self-assembly depends on the compression rate. Slow compression approximates equilibrium results, while fast compression can skip intermediate structures. Crossovers for which no continuous line-slip exists are found to be dynamically unfavorable, which is the source of this difference. Results from colloidal sedimentation experiments at high P\'eclet number are found to be consistent with the results of fast compressions, as long as appropriate boundary conditions are used. The similitude between compression and sedimentation results suggests that the assembly pathway does not here sensitively depend on the nature of the out-of-equilibrium dynamics.Item Open Access Breaking the glass ceiling: Configurational entropy measurements in extremely supercooled liquids(2017-06-01) Berthier, Ludovic; Charbonneau, Patrick; Coslovich, Daniele; Ninarello, Andrea; Ozawa, M; Yaida, ShoLiquids relax extremely slowly on approaching the glass state. One explanation is that an entropy crisis, due to the rarefaction of available states, makes it increasingly arduous to reach equilibrium in that regime. Validating this scenario is challenging, because experiments offer limited resolution, while numerical studies lag more than eight orders of magnitude behind experimentally-relevant timescales. In this work we not only close the colossal gap between experiments and simulations but manage to create in-silico configurations that have no experimental analog yet. Deploying a range of computational tools, we obtain four estimates of their configurational entropy. These measurements consistently confirm that the steep entropy decrease observed in experiments is found also in simulations even beyond the experimental glass transition. Our numerical results thus open a new observational window into the physics of glasses and reinforce the relevance of an entropy crisis for understanding their formation.Item Open Access Bypassing sluggishness: SWAP algorithm and glassiness in high dimensionsBerthier, Ludovic; Charbonneau, Patrick; Kundu, JoyjitThe recent implementation of a swap Monte Carlo algorithm (SWAP) for polydisperse mixtures fully bypasses computational sluggishness and closes the gap between experimental and simulation timescales in physical dimensions $d=2$ and $3$. Here, we consider suitably optimized systems in $d=2, 3,\dots, 8$, to obtain insights into the performance and underlying physics of SWAP. We show that the speedup obtained decays rapidly with increasing the dimension. SWAP nonetheless delays systematically the onset of the activated dynamics by an amount that remains finite in the limit $d \to \infty$. This shows that the glassy dynamics in high dimensions $d>3$ is now computationally accessible using SWAP, thus opening the door for the systematic consideration of finite-dimensional deviations from the mean-field description.Item Open Access Characterization and efficient Monte Carlo sampling of disordered microphases.(The Journal of chemical physics, 2021-06) Zheng, Mingyuan; Charbonneau, PatrickThe disordered microphases that develop in the high-temperature phase of systems with competing short-range attractive and long-range repulsive (SALR) interactions result in a rich array of distinct morphologies, such as cluster, void cluster, and percolated (gel-like) fluids. These different structural regimes exhibit complex relaxation dynamics with marked heterogeneity and slowdown. The overall relationship between these structures and configurational sampling schemes, however, remains largely uncharted. Here, the disordered microphases of a schematic SALR model are thoroughly characterized, and structural relaxation functions adapted to each regime are devised. The sampling efficiency of various advanced Monte Carlo sampling schemes-Virtual-Move (VMMC), Aggregation-Volume-Bias (AVBMC), and Event-Chain (ECMC)-is then assessed. A combination of VMMC and AVBMC is found to be computationally most efficient for cluster fluids and ECMC to become relatively more efficient as density increases. These results offer a complete description of the equilibrium disordered phase of a simple microphase former as well as dynamical benchmarks for other sampling schemes.Item Open Access Clustering and assembly dynamics of a one-dimensional microphase former.(Soft matter, 2018-03-26) Hu, Yi; Charbonneau, PatrickBoth ordered and disordered microphases ubiquitously form in suspensions of particles that interact through competing short-range attraction and long-range repulsion (SALR). While ordered microphases are more appealing materials targets, understanding the rich structural and dynamical properties of their disordered counterparts is essential to controlling their mesoscale assembly. Here, we study the disordered regime of a one-dimensional (1D) SALR model, whose simplicity enables detailed analysis by transfer matrices and Monte Carlo simulations. We first characterize the signature of the clustering process on macroscopic observables, and then assess the equilibration dynamics of various simulation algorithms. We notably find that cluster moves markedly accelerate the mixing time, but that event chains are of limited help in the clustering regime. These insights will inspire further study of three-dimensional microphase formers.Item Open Access Comment on "kosterlitz-Thouless-type caging-uncaging transition in a quasi-one-dimensional hard disk system"(Physical Review Research, 2021-09-01) Hu, Y; Charbonneau, PHuerta [Phys. Rev. Research 2, 033351 (2020)2643-156410.1103/PhysRevResearch.2.033351] report a power-law decay of positional order in numerical simulations of hard disks confined within hard parallel walls, which they interpret as a Kosterlitz-Thouless (KT)-type caging-uncaging transition. The proposed existence of such a transition in a quasi-one-dimensional system, however, contradicts long-held physical expectations. To clarify if the proposed ordering persists in the thermodynamic limit, we introduce an exact transfer matrix approach to expeditiously generate configurations of very large subsystems that are typical of equilibrium thermodynamic (infinite-size) systems. The power-law decay of positional order is found to extend only over finite distances. We conclude that the numerical simulation results reported are associated with a crossover unrelated to KT-type physics, and not with a proper thermodynamic phase transition.Item Open Access Correlation lengths in quasi-one-dimensional systems via transfer matrices(Molecular Physics, 2018-06) Hu, Y; Fu, L; Charbonneau, P© 2018 Informa UK Limited, trading as Taylor & Francis Group. Using transfer matrices up to next-nearest-neighbour interactions, we examine the structural correlations of quasi-one-dimensional systems of hard disks confined by two parallel lines and hard spheres confined in cylinders. Simulations have shown that the non-monotonic and non-smooth growth of the correlation length in these systems accompanies structural crossovers [Fu et al., Soft Matter 13, 3296 (2017)]. Here, we identify the theoretical basis for these behaviours. In particular, we associate kinks in the growth of correlation lengths with eigenvalue crossing and splitting. Understanding the origin of such structural crossovers answers questions raised by earlier studies, and thus bridges the gap between theory and simulations for these reference models.Item Open Access Finite Dimensional Vestige of Spinodal Criticality above the Dynamical Glass Transition.(Physical review letters, 2020-09) Berthier, Ludovic; Charbonneau, Patrick; Kundu, JoyjitFinite dimensional signatures of spinodal criticality are notoriously difficult to come by. The dynamical transition of glass-forming liquids, first described by mode-coupling theory, is a spinodal instability preempted by thermally activated processes that also limit how close the instability can be approached. We combine numerical tools to directly observe vestiges of the spinodal criticality in finite dimensional glass formers. We use the swap Monte Carlo algorithm to efficiently thermalize configurations beyond the mode-coupling crossover, and analyze their dynamics using a scheme to screen out activated processes, in spatial dimensions ranging from d=3 to d=10. We observe a strong softening of the mean-field square-root singularity in d=3 that is progressively restored as d increases above d=8, in surprisingly good agreement with perturbation theory.Item Open Access Finite-size effects in the microscopic critical properties of jammed configurations: A comprehensive study of the effects of different types of disorder.(Physical review. E, 2021-07) Charbonneau, Patrick; Corwin, Eric I; Dennis, R Cameron; Díaz Hernández Rojas, Rafael; Ikeda, Harukuni; Parisi, Giorgio; Ricci-Tersenghi, FedericoJamming criticality defines a universality class that includes systems as diverse as glasses, colloids, foams, amorphous solids, constraint satisfaction problems, neural networks, etc. A particularly interesting feature of this class is that small interparticle forces (f) and gaps (h) are distributed according to nontrivial power laws. A recently developed mean-field (MF) theory predicts the characteristic exponents of these distributions in the limit of very high spatial dimension, d→∞ and, remarkably, their values seemingly agree with numerical estimates in physically relevant dimensions, d=2 and 3. These exponents are further connected through a pair of inequalities derived from stability conditions, and both theoretical predictions and previous numerical investigations suggest that these inequalities are saturated. Systems at the jamming point are thus only marginally stable. Despite the key physical role played by these exponents, their systematic evaluation has yet to be attempted. Here, we carefully test their value by analyzing the finite-size scaling of the distributions of f and h for various particle-based models for jamming. Both dimension and the direction of approach to the jamming point are also considered. We show that, in all models, finite-size effects are much more pronounced in the distribution of h than in that of f. We thus conclude that gaps are correlated over considerably longer scales than forces. Additionally, remarkable agreement with MF predictions is obtained in all but one model, namely near-crystalline packings. Our results thus help to better delineate the domain of the jamming universality class. We furthermore uncover a secondary linear regime in the distribution tails of both f and h. This surprisingly robust feature is understood to follow from the (near) isostaticity of our configurations.Item Open Access Gardner Phenomenology in Minimally Polydisperse Crystalline SystemsCharbonneau, Patrick; Corwin, Eric I; Fu, Lin; Tsekenis, Georgios; van der Naald, MichaelWe study the structure and dynamics of crystals of minimally polydisperse hard spheres at high pressures. Structurally, they exhibit a power-law scaling in their probability distribution of weak forces and small interparticle gaps as well as a flat density of vibrational states. Dynamically, they display anomalous aging beyond a characteristic pressure. Although essentially crystalline, these solids thus display features reminiscent of the Gardner phase observed in certain amorphous solids. Because preparing these materials is fast and facile, they are ideal for testing a theory of amorphous materials. They are also amenable to experimental realizations in commercially-available particulate systems.Item Open Access Granular Impact Dynamics: Acoustics and FluctuationsClark, Abram H; Behringer, RPIn the corresponding fluid dynamics video, created for the APS DFD 2012 Gallery of Fluid Motion, we show high-speed videos of 2D granular impact experiments, where an intruder strikes a collection of bidisperse photoelastic disks from above. We discuss the force beneath the intruder, which is strongly fluctuating in space and time. These fluctuations correspond to acoustic pulses which propagate into the medium. Analysis shows that this process, in our experiments, is dominated by collisions with grain clusters. The energy from these collisions is carried into the granular medium along networks of grains, where is it dissipated.Item Open Access How to create equilibrium vapor-deposited glasses(2017-08-23) Berthier, Ludovic; Charbonneau, Patrick; Flenner, E; Zamponi, FrancescoGlass films created by vapor-depositing molecules onto a substrate can exhibit properties similar to those of ordinary glasses aged for thousands of years. It is believed that enhanced surface mobility is the mechanism that allows vapor deposition to create such exceptional glasses, but it is unclear how this effect is related to the final state of the film. Here we use molecular dynamics simulations to model vapor deposition and an efficient Monte Carlo algorithm to determine the deposition rate needed to create equilibrium glassy films. We obtain a scaling relation that quantitatively captures the efficiency gain of vapor deposition over bulk annealing, and demonstrates that surface relaxation plays the same role in the formation of vapor-deposited glasses as bulk relaxation in ordinary glass formation.Item Open Access Local dynamical heterogeneity in glass formers(2021-09-24) Biroli, Giulio; Charbonneau, Patrick; Folena, Giampaolo; Hu, Yi; Zamponi, FrancescoWe study the local dynamical fluctuations in glass-forming models of particles embedded in $d$-dimensional space, in the mean-field limit of $d\to\infty$. Our analytical calculation reveals that single-particle observables, such as squared particle displacements, display divergent fluctuations around the dynamical (or mode-coupling) transition, due to the emergence of nontrivial correlations between displacements along different directions. This effect notably gives rise to a divergent non-Gaussian parameter, $\alpha_2$. The $d\to\infty$ local dynamics therefore becomes quite rich upon approaching the glass transition. The finite-$d$ remnant of this phenomenon further provides a long sought-after, first-principle explanation for the growth of $\alpha_2$ around the glass transition that is \emph{not based on multi-particle correlations}.Item Open Access MC-DEM: a novel simulation scheme for modeling dense granular mediaBehringer, Robert P; Brodu, N; Dijksman, JAThis article presents a new force model for performing quantitative simulations of dense granular materials. Interactions between multiple contacts (MC) on the same grain are explicitly taken into account. Our readily applicable method retains all the advantages of discrete element method (DEM) simulations and does not require the use of costly finite element methods. The new model closely reproduces our recent experimental measurements, including contact force distributions in full 3D, at all compression levels up to the experimental maximum limit of 13\%. Comparisons with traditional non-deformable spheres approach are provided, as well as with alternative models for interactions between multiple contacts. The success of our model compared to these alternatives demonstrates that interactions between multiple contacts on each grain must be included for dense granular packings.Item Open Access Mean-Field Caging in a Random Lorentz Gas.(The journal of physical chemistry. B, 2021-06-07) Biroli, Giulio; Charbonneau, Patrick; Hu, Yi; Ikeda, Harukuni; Szamel, Grzegorz; Zamponi, FrancescoThe random Lorentz gas (RLG) is a minimal model of both percolation and glassiness, which leads to a paradox in the infinite-dimensional,*d*→ ∞ limit: the localization transition is then expected to be*continuous*for the former and*discontinuous*for the latter. As a putative resolution, we have recently suggested that, as*d*increases, the behavior of the RLG converges to the glassy description and that percolation physics is recovered thanks to finite-*d*perturbative and nonperturbative (instantonic) corrections [Biroli et al.*Phys. Rev. E*2021, 103, L030104]. Here, we expand on the*d*→ ∞ physics by considering a simpler static solution as well as the dynamical solution of the RLG. Comparing the 1/*d*correction of this solution with numerical results reveals that even perturbative corrections fall out of reach of existing theoretical descriptions. Comparing the dynamical solution with the mode-coupling theory (MCT) results further reveals that, although key quantitative features of MCT are far off the mark, it does properly capture the discontinuous nature of the*d*→ ∞ RLG. These insights help chart a path toward a complete description of finite-dimensional glasses.Item Open Access Memory Formation in Jammed Hard Spheres.(Physical review letters, 2021-02) Charbonneau, Patrick; Morse, Peter KLiquids equilibrated below an onset condition share similar inherent states, while those above that onset have inherent states that markedly differ. Although this type of materials memory was first reported in simulations over 20 years ago, its physical origin remains controversial. Its absence from mean-field descriptions, in particular, has long cast doubt on its thermodynamic relevance. Motivated by a recent theoretical proposal, we reassess the onset phenomenology in simulations using a fast hard sphere jamming algorithm and find it to be both thermodynamically and dimensionally robust. Remarkably, we also uncover a second type of memory associated with a Gardner-like regime of the jamming algorithm.Item Open Access Microphase Equilibrium and Assembly Dynamics(2017-08-23) Zhuang, Yuan; Charbonneau, PatrickDespite many attempts, ordered equilibrium microphases have yet to be obtained in experimental colloidal suspensions. The recent computation of the equilibrium phase diagram of a microscopic, particle-based microphase former [Zhuang et al., Phys. Rev. Lett. 116, 098301 (2016)] has nonetheless found such mesoscale assemblies to be thermodynamically stable. Here, we consider their equilibrium and assembly dynamics. At intermediate densities above the order-disorder transition, we identify four different dynamical regimes and the structural changes that underlie the dynamical crossovers from one disordered regime to the next. Below the order-disorder transition, we also find that periodic lamellae are the most dynamically accessible of the periodic microphases. Our analysis thus offers a comprehensive view of the disordered microphase dynamics and a route to the assembly of periodic microphases in a putative well-controlled, experimental system.Item Open Access Numerical transfer matrix study of frustrated next-nearest-neighbor Ising models on square lattices(Physical Review B, 2021-10-01) Hu, Y; Charbonneau, PIsing models with frustrated next-nearest-neighbor interactions present a rich array of modulated phases. These phases, however, assemble and relax slowly, which hinders their computational study. In two dimensions, strong fluctuations further hamper determining their equilibrium phase behavior from theoretical approximations. The exact numerical transfer matrix (TM) method, which bypasses both difficulties, can serve as a benchmark method once its own numerical challenges are surmounted. Building on our recent study [Hu and Charbonneau, Phys. Rev. B 103, 094441 (2021)2469-995010.1103/PhysRevB.103.094441], in which we evaluated the two-dimensional axial next-nearest-neighbor Ising model with transfer matrices, we here extend the effective usage of the TM method to Ising models with biaxial, diagonal, and third-nearest-neighbor frustration models. The high-accuracy TM numerics help resolve various physical ambiguities about these reference models, thus providing a clearer overview of modulated phase formation in two dimensions.Item Open Access Origin of Ultrastability in Vapor-Deposited Glasses.(Physical review letters, 2017-11) Berthier, Ludovic; Charbonneau, Patrick; Flenner, Elijah; Zamponi, FrancescoGlass films created by vapor-depositing molecules onto a substrate can exhibit properties similar to those of ordinary glasses aged for thousands of years. It is believed that enhanced surface mobility is the mechanism that allows vapor deposition to create such exceptional glasses, but it is unclear how this effect is related to the final state of the film. Here we use molecular dynamics simulations to model vapor deposition and an efficient Monte Carlo algorithm to determine the deposition rate needed to create ultrastable glassy films. We obtain a scaling relation that quantitatively captures the efficiency gain of vapor deposition over bulk annealing, and demonstrates that surface relaxation plays the same role in the formation of vapor-deposited glasses as bulk relaxation does in ordinary glass formation.