Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Q08: Jamming and Glassy BehaviorRecordings Available
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Sponsoring Units: GSNP Chair: Daniel Sussman, Emory University Room: McCormick Place W-179B |
Wednesday, March 16, 2022 3:00PM - 3:12PM |
Q08.00001: Influence of particle size distribution on 2D random close packing Eric R Weeks The densest amorphous packing of rigid particles is known as random close packing (RCP). It is well known that higher RCP volume fractions are achieved by using collections of particles with a variety of sizes. The variety of sizes is often quantified by the polydispersity of the particle size distribution: the standard deviation of the radius divided by the mean radius. Our prior work showed that for 3D packings, the skewness also plays an important role (related to the third moment of the size distribution). In this talk, we present results from 2D packings with a variety of size distributions. The behavior is somewhat different from the 3D results, but again we present an empirical formula that describes the RCP volume fraction data well across the variety of size distributions. |
Wednesday, March 16, 2022 3:12PM - 3:24PM |
Q08.00002: Structure of ellipses and ellipsoids at their RSA densities Robert S Hoy, Pedro Abritta Motivated by the recent observation of liquid glass in suspensions of ellipsoidal colloids [J. Roller et al, Proc. Nat. Acad. Sci. 118, e2018072118 (2018)], we examine the structure of ellipses and prolate ellipsoids at their random sequential addition densities φs(α,d), where α is particle aspect ratio and d is spatial dimension. φs(α,d) is the maximum density at which these systems can be prepared with no correlation of particles’ positions or orientations save that required by 2-body impenetrability constraints. The differences φg(α,d) - φs(α,d) and φMRJ(α,d) - φs(α,d) are of particular interest because they indicate how much packing efficiency can be gained (before glass formation and jamming, respectively) by allowing particles to translate and rotate freely while remaining positionally and orientationally disordered. We determine φs(α,d) for a wider range of α (and to considerably higher precision for all α) than had been previously reported, explore in detail how these maximally dense and random states’ structure varies with α and d, and attempt to connect our findings to α- and d-dependent trends in these systems’ jamming behavior. |
Wednesday, March 16, 2022 3:24PM - 3:36PM |
Q08.00003: Criticality and marginal stability of shear driven jamming in frictionless sphere packings. Srikanth Sastry, Varghese Babu |
Wednesday, March 16, 2022 3:36PM - 3:48PM Withdrawn |
Q08.00004: Stress Fluctuations in Driven Packings of Partially Saturated Granular Media Tanvi Gandhi, Qinghao Mao, Heinrich M Jaeger A granular packing compressed past its yielding point undergoes localized rearrangements which appear as stress drops in bulk stress-strain measurements. Previous research has demonstrated that the stress fluctuation behavior in dry granular materials is highly dependent on particle surface roughness and particle shape, and can be quantified using volatility, a measure of fluctuations borrowed from financial mathematics [1, 2]. Except in the case of smooth spheres, the behavior of driven granular systems in partial saturation remains poorly understood, and little work has been done on studying their fluctuation behavior. We investigate the volatility and shear strength in packings where the surfaces of 3D-printed grains are modified by the presence of a wetting fluid. We further discuss the dependence of the effective friction in such a packing on particle shape. Probing the local rearrangements provides insights about the intergranular forces supplied by these additives and presents a useful handle for tuning the mechanical responses of granular materials. |
Wednesday, March 16, 2022 3:48PM - 4:00PM |
Q08.00005: Deep supercooling of Hard-Sphere fluids using metadynamics sampling John C Crocker, Amruthesh Thirumalaiswamy, Robert Riggleman Hard-sphere fluids (and their soft-sphere cousins) have proven very fruitful models for understanding the glass and jamming transitions. Previous studies have identified polydisperse sphere fluids that completely avoid crystallization, and using state of the art methods such as swap Monte Carlo, equilibrated them up to unprecedented high volume fractions well above the glass transition. Outstanding questions include the existence of a Kauzmann density above which the entropy of the equilibrium fluid becomes sub-extensive, and the nature of jammed states above that density. Here we use a metadynamics-inspired sampling method to efficiently equilibrate HS fluids at very high volume fractions. Unlike conventional `basin-filling' metadynamics that operates on a reduced dimensional space, we operate in the full 3N-dimensional configuration space of the fluid. Remarkably, we find that within a small window of bias potential properties, HS fluid configurations rapidly equilibrate under biased relaxation. The rate of such relaxation is only weakly sensitive to volume fraction. The observed fluid states have a pressure that is well described by the Carnahan-Starling equation of state up to the highest volume fraction we studied, Φ = 0.670. Curiously, such deeply supercooled HS fluids are difficult to compress using conventional jamming approaches. |
Wednesday, March 16, 2022 4:00PM - 4:12PM |
Q08.00006: Jamming Hard-Spheres configurations through Iterative Linear Optimization Rafael Diaz Hernandez Rojas, Giorgio Parisi, Federico Ricci Tersenghi, Claudia Artiaco It has recently been discovered that jamming criticality of spheres-based models defines a broad universality class. Yet, computational techniques to produce jammed packings are still somewhat limited. Moreover, most of available methods are based on energy minimization algorithms, and are therefore designed for soft-spheres configurations. Consequently, generating a critical jammed packing of hard-spheres (HS) is further complicated due to the singular interaction between such type of particles. Here, we present an algorithm that allows to reach the jamming point of HS configurations in arbitrary dimensions, through a series of linear optimization problems. Within our approach, the exact, non-convex optimization problem associated to jamming of HS is replaced by a sequence of simpler linear problems. Nevertheless, in all cases the non-overlapping constraints imposed by the HS interaction are strictly satisfied. Importantly, we prove that upon convergence our algorithm produces a stable, well defined jammed state of HS, that corresponds to a (possibly local) optimum of the exact problem. We also show that our method allows to easily construct the full network of contact forces from the Lagrange multipliers associated to the non-overlapping constraints. |
Wednesday, March 16, 2022 4:12PM - 4:24PM |
Q08.00007: Efficient high-dimensional molecular dynamics for studies of the glass/jamming transition Robert S Hoy Many of the most exciting recent advances in the theory of amorphous materials have come from studies of high-dimensional liquids. Simulations of such liquids, however, have been limited by the lack of a publicly-available, open-source, efficiently-parallel molecular dynamics code that works for d > 3. We have developed such a code (hdMD). All its routines work in arbitrary d; the maximum simulated d is limited only by available computing resources. These routines include several that are particularly useful for studies of the glass/jamming transition, such as SWAP Monte Carlo and FIRE energy minimization. Scaling of simulation runtimes with the number of particles N and number of simulation threads nthreads is comparable to popular MD codes such as LAMMPS, and the latter scaling actually improves with increasing d. This efficient parallel implementation allows simulation of systems that are much larger than those employed in previous high-dimensional studies. As a demonstration of the code's capabilities, we show that dynamics in d = 6 supercooled liquids can be much more heterogeneous than previously reported. |
Wednesday, March 16, 2022 4:24PM - 4:36PM |
Q08.00008: Non-trivial roles of multi-particle correlations in fragile glass formers Chengjie Luo, Liesbeth Janssen It is widely believed that the emergence of slow glassy dynamics is encoded in a material's microstructure. For fragile glass formers such as the archetypical hard-sphere model, the static structure factor, i.e., the static two-point density correlation, is usually assumed to be sufficient to describe all relevant structural features that give rise to glassy dynamics. We challenge this status quo by studying a binary hard-sphere mixture with a first-principles-based theory that can systematically take higher-order static and dynamic correlations into account. We find that only including the static triplet direct correlations already changes the prediction of the glass-transition diagram both qualitatively and quantitatively. The diagram is also tremendously affected by increasing the order of the dynamic multi-point density correlations in the theory. Hence, even for simple fragile materials, the conventionally neglected static triplet direct correlations as well as the higher order static and dynamic correlations are in fact non-negligible. |
Wednesday, March 16, 2022 4:36PM - 4:48PM |
Q08.00009: Inherent state memory as a probe for non-equilibrium Gardner physics in thermal soft spheres Robert S Hoy, Kevin Interiano Alberto, Peter K Morse, Patrick Charbonneau The Gardner transition, located deep within the glass phase, denotes a topological change in the (effective) free energy landscape of a glass from smooth to rough. The saddle points inherent to this change lead to a marked dynamical slowdown and to growing correlation lengths. Until recently, the Gardner transition had only been characterized in equilibrium or quasi-equilibrium systems near jamming, and thus its experimental observation would have required enormous time scales and high instrumental accuracy. However, recent work has shown that Gardner-related signatures also emerge when a dense liquid or glass is rapidly quenched towards the nearest jammed configuration. In this talk, we demonstrate the existence of an out-of-equilibrium Gardner transition in a nearly-hard-sphere liquid that manifests in: (i) a divergence in the time required for energy minimization, (ii) the onset of a large susceptibility, and (iii) the onset of rattler identity changes. The last of these effects, in particular, should be experimentally accessible. |
Wednesday, March 16, 2022 4:48PM - 5:00PM |
Q08.00010: Extracting universal scaling functions of rigidity transitions from an effective medium theory Stephen J Thornton, Danilo B Liarte, James P Sethna Rigidity transitions in random systems, such as jamming (J) and rigidity percolation (RP), have long evaded description by the usual framework of critical phenomena. The coherent potential approximation (CPA), a type of effective medium theory, has served in the past as a valuable tool to predict dynamics and transition points in randomly percolated lattices. We leverage the analytically tractable self-consistency equations for the self-energy in the CPA to express physically observable quantities, such as frequency-dependent viscoelastic moduli and correlation functions, in the usual scaling framework of critical phenomena [1]. We find the scaling behavior of these transitions in two spatial dimensions to be modified from that of higher dimensions – including a dangerous irrelevant variable that modifies the low-energy physics and logarithms that appear in the scaling functions [2]. |
Wednesday, March 16, 2022 5:00PM - 5:12PM |
Q08.00011: Four-point functions in glass-forming liquids: what information do they encode Horacio E Castillo We examine the four-point functions describing dynamic heterogeneity in glass-forming liquids and show how contributions with different physical origins can be identified and determined. Collective relaxation fluctuations constitute only one of the contributions to the four-point functions, but this contribution can be cleanly extracted in certain time regimes. This provides a way to determine the exchange time describing the persistence of faster and slower relaxing regions in dynamically heterogeneous systems. |
Wednesday, March 16, 2022 5:12PM - 5:24PM |
Q08.00012: Spectral Physics of Spin Glasses Michael Winer, Brian Swingle, Christopher Baldwin, Richard D Barney It is widely established that fast-thermalizing chaotic systems exhibit random-matrix-like statistics in their energy level spacings, while integrable systems exhibit Poissonian statistics. In this paper we investigate a third class of systems: spin glasses. These systems are chaotic don't achieve full thermalization due to energy or entropy barriers between regions of phase space. We examine their spectral statistics analytically using a mean-field theory approach, and find statistics consistent with independent random matrices for each connected component of the phase space. Our techniques show that spectral statistics are sensitive to this ergodicity breaking, and can be generalized to diagnose glassiness in strongly quantum systems without a classical analog, as well as proving novel results about the complexity distribution in our toy model. |
Wednesday, March 16, 2022 5:24PM - 5:36PM |
Q08.00013: Numerical evidence for rejuvenation in simulation that mimics the experimental protocol of the Thermoremanent and Zero-Field Cooling Ilaria Paga The scaling law introduced in Ref.[1-2] solved a three-decade problem concerning the nature of the Zeeman energy [3-4]. The dynamical arrest found upon cooling glass formers to their glass temperature $T_\mathrm{g}$ is explained in terms of the correlation length $\xi$ which is used as a caliper for the magnetic response both in simulations and experiments. We study the non-equilibrium spin-glass dynamics in a large-scale simulation of the Ising-Edwards-Anderson (IEA) model carried out on the Janus~II custom-built supercomputer [5]. We unveil differences between the experimental Thermoremanent protocol (TRM) and the Zero-Field Cooling (ZFC) one. For the first time, we observe the rejuvenation effect in simulations and we use these protocols to search for memory and rejuvenation effects,[6]. |
Wednesday, March 16, 2022 5:36PM - 5:48PM |
Q08.00014: Continious Random Network Avoidance and Microscopic Relaxation Time in As2Se3 glass. Chris B Nelson Recent nuclear magnetic resonance (NMR) studies on SiO2 structural glass has shown a positive correlation exists between Si-O bond lengths and Si-O-Si bond angles. This indicates that when the glass solidified it avoided forming as a continuous random network (CRN). A microscopic tight binding (TB) model was used some years ago to predict the nuclear quadrupole resonance (NQR) distribution of powdered As2Se3 glass. Similar bond length- bond angle correlations were found. Here we extend this model and show that these correlations are directly attributable to a competition between valence electronic energy and emergent frustration forces as the glass solidifies into a locally preferred structure (LPS). Recent studies have shown that fast atomic motion occurs in metallic glasses at temperatures far below the glass temperature. Using this model we calculate a microscopic relaxation time and show it is a product of CRN avoidance. |
Wednesday, March 16, 2022 5:48PM - 6:00PM |
Q08.00015: Analytic continuation over complex landscapes Jaron Kent-Dobias, Jorge Kurchan Energy landscapes with a superextensive number of stationary points appear in models of structural and spin glasses, data science, strongly correlated electron systems, and string theory. In spin glasses, a lot is known about the structure of generic random landscapes made from real polynomials. Little is known about complex landscapes of complex variables, which appear explicitly in models of random lasers and quantum systems and implicitly in the analytic continuation of classical glasses. In the real case the statistics of stationary points by their energy and their number of unstable directions informs dynamics and geometry. In the complex case all stationary points are saddles with the same number of unstable directions, and whether their spectrum is gapped determines their local geometry. We describe what different landscape structures imply for analytic continuation. |
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