Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session N16: Disordered and Glassy Systems (Non-polymeric) |
Hide Abstracts |
Sponsoring Units: DSOFT Chair: Peter Morse, Duke University Room: Room 208 |
Wednesday, March 8, 2023 11:30AM - 11:42AM |
N16.00001: A Theory of High-Temperature Arrhenius Relaxation in Two-Dimensional Glass-forming Liquids Muhammad R Hasyim, Kranthi K Mandadapu The relaxation time of dense liquids is Arrhenius at a wide range of temperatures, including glass-forming liquids above the onset temperature $T_o$ for glassy dynamics. Below $T_o$, one may invoke dynamical facilitation theory to understand dynamics via spatially localized excitations, which drive relaxation through the facilitation of nearby excitations. In this talk, we discuss a theory for Arrhenius relaxation above $T_o$, where excitations emerge without facilitation as localized pure-shear events [1]. The theory builds upon recent work [2] that describes the onset of glassy dynamics as a melting transition, where supercooled liquids lose their inherent rigidity due to excitation softening. In two dimensions (2D), this scenario is similar to the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) scenario for melting in 2D solids [3]. The KTHNY scenario implies critical fluctuations near $T_o$ that renormalize the shear modulus, which affects the excitation activation energy $E_a$. We model how excitations emerge without facilitation via a Poisson point process, allowing us to connect $E_a$ to the Arrhenius relaxation time and derive the logarithmic finite-size scaling in diffusivity. The predicted activation energies agree with those obtained from simulations of 2D model glass formers. These results provide a basis for localized excitations appearing above but close to $T_o$ and strengthen the role of such excitations for broadly understanding dynamics in glass-forming liquids. |
Wednesday, March 8, 2023 11:42AM - 11:54AM |
N16.00002: A microscopic theory of an equation of thixotropy from the dynamics of stress distributions in soft particle glasses. Minaspi Bantawa, Roger T. Bonnecaze The jammed suspensions of soft particle glasses (SPGs) exhibit interesting rheological response under start-up shear flow. Macroscopic measurements indicate SPGs "remember" their past history. We hypothesize that the rheology of SPGs is sensitive to the applied shear rate and shear history which manifest in the different microscopic rearrangements of individual particles and their contribution to the total stress. Using large scale 3D numerical simulations of model SPGs, we show that shear induced microstructural rearrangements at different points in the stress-strain curve result in distinct distributions of local stresses, which impact the overall rheological response. Interestingly, suspensions with the same microscopic stress can have very different distributions of stress locally. Although distributions of stresses vary locally, long-ranged correlations are not observed. We demonstrate that the evolution of stress distribution under start-up flow leads to the equation of thixotropy which can predict the rheological response and recover the macroscopic rheological measurements. |
Wednesday, March 8, 2023 11:54AM - 12:06PM |
N16.00003: Excitation-facilitated hops play a dominant role in relaxation and transport of liquids even above TA Marcus T Cicerone, Jesse McDaniel It is widely believed that particle hopping is an important mechanism for transport and relaxation in the supercooled and glassy regimes of liquids. Using commonly employed methods to identify hops in real space, they are not evident at high temperatures (above TA), where relaxation follows an Arrhenius law, and are thus thought to be unimportant above this temperature. Employing reciprocal space analysis through the intermediate scattering function we not only identify excitations and hops above TA, we show that they are also a central relaxation and transport pathway in this high-temperature range. |
Wednesday, March 8, 2023 12:06PM - 12:18PM |
N16.00004: The Advantage of A Structural Channel in the Dynamical Response of Elastoplastic Models Robert C Dennis, Andrea J Liu, M. Lisa Manning As it pertains to failure in mechanically driven crystalline solids, the sites that undergo the bulk of rearrangement are easily identifiable as defects. However, in disordered systems such as glasses, the sites that are likely to rearrange, termed soft spots, are much more difficult to predict and involve rich and complex avalanche dynamics. Beyond being able to better predict avalanches, improving our understanding of these dynamics will also aid in designing better materials. While simplified elastoplastic models have been successful in furthering our understanding of avalanches, it has been shown that they do not display the same spatial correlations as sheared granular solids. Because predicting soft spots from the structure of the material has been widely successful, the Structuro-Elasto-Plasticity Model (StEP) was created to include a separate structural channel for the likelihood of cells to rearrange. We demonstrate the advantage of this elastoplastic model, not only regarding the rearrangement statistics, but the avalanche dynamics as well. |
Wednesday, March 8, 2023 12:18PM - 12:30PM |
N16.00005: Inherent-State Melting and the Onset of Glassy Dynamics in Two-Dimensional Supercooled Liquids Dimitrios Fraggedakis, Muhammad R Hasyim, Kranthi K Mandadapu Below the onset temperature To, most glass formers are characterized by the super-Arrhenius temperature dependence of their equilibrium relaxation time. In this supercooled regime, the relaxation dynamics also proceeds through localized elastic excitations [1] corresponding to hopping events between inherent states. Despite its importance in distinguishing the supercooled regime from the high-temperature regime, the microscopic origin of To is not yet known. Here, we construct a theory for the onset temperature in two dimensions [2] and find that a binding-unbinding transition of dipolar elastic excitations, analogous to the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) theory, describes the transition from the supercooled regime to the high-temperature one. The predicted transition temperature agrees with the onset temperature found in various two-dimensional (2D) atomistic models of glass formers and an experimental binary colloidal system confined to a water-air interface [3]. We further find the predictions for the renormalized elastic moduli to agree with the experimentally observed values below To for the latter 2D colloidal system. |
Wednesday, March 8, 2023 12:30PM - 12:42PM |
N16.00006: Elasticity and criticality in pruned prestressed disordered networks Marco Aurelio Galvani Cunha, John C Crocker, Andrea J Liu Unstressed disordered central-force spring networks are stable above and floppy below a critical coordination given by the Maxwell isostaticity criterion. It has been shown that one can tune the Poisson ratio of such networks to any value in its allowed range by selectively pruning a small fraction of the bonds as one approaches the limit of mechanical stability. Here we ask how tuning the Poisson ratio by pruning bonds is altered by the existence of prestresses on the network. We show that the response to pruning is altered completely and that the degree of tunability is highly influenced by the nature of the prestress. |
Wednesday, March 8, 2023 12:42PM - 12:54PM |
N16.00007: The surprising utility of excess entropy in the study of supercooled liquids Ian R Graham, Paulo E Arratia, Robert A Riggleman In equilibrium liquids, excess entropy shows a surprising effectiveness in correlating with the dynamical properties of many computational liquids, yielding a simple scaling relation that collapses the trends observed across these systems known as Rosenfeld scaling. Thus, the dynamics seen in these equilibrated systems can be inferred directly from a thermodynamic quantity. In supercooled liquids however, this simple relationship breaks down, and the common two-body approximation for the excess entropy is insufficient to predict average particle mobilities. In this work we analyze a variety of binary Lennard-Jones mixtures to explore the utility of excess entropy in the supercooled regime. We find that under proper partitioning of systems by their rearrangement dynamics, we can collapse the dynamical properties of these ensembles across systems as a function of excess entropy. We show how the barriers for rearrangement change with the shape of the pair potential and interpret how these changes are related to the stiffness of the potential. |
Wednesday, March 8, 2023 12:54PM - 1:06PM |
N16.00008: Random Close Packing is least random in 3D Ashley Z Guo, Sam Wilken, Dov Levine, Paul M Chaikin Biased Random Organization (BRO) is a simple dynamical model that produces hyperuniform Random Close Packed (RCP) structures at its critical endpoint in 3D. BRO follows Manna universality class behavior, with an upper critical dimension of 4. We confirm mean field exponents for d≥4 through analysis of the fraction of active states and the distribution of interparticle gaps. Through simulations, we show that monodisperse BRO systems in d=3,4,5 recover RCP behavior at their critical endpoint with previously predicted packing fractions of φ=0.64, 0.45, and 0.30 respectively. Additionally, we find BRO in d=3,4,5 produces structures with their corresponding isostatic contact numbers Z=6, 8, and 10. While bidisperse BRO in 2D produces hyperuniform and isostatic critical states, the monodisperse case instead produces a crystalline state as its critical endpoint. This leads us to conjecture that BRO produces RCP as its critical endpoint in any dimension, suggesting that there is no RCP for monodisperse disks in 2D. Furthermore, we show that density fluctuations are random rather than hyperuniform in the mean field regime, S(q→0)~q0, leaving hyperuniformity to only be observed in 3D, S(q→0)~q0.25. |
Wednesday, March 8, 2023 1:06PM - 1:18PM |
N16.00009: Ultrastable states in Jammed Packings: Characterization and Construction Sascha Hilgenfeldt, Sangwoo Kim Jammed packings serve as model systems for the structure and mechanical behavior of disordered assemblies of particles, from colloids to glassy solids. A recent focus has been on the detection and characterization of structures with unusual, exceptional properties such as strongly enhanced stability with respect to imposed strain. In simulations of overjammed polydisperse 2D packings of soft disks, we identify such rare, ultrastable states via an order parameter that quantifies the closeness of the structure to a sterically optimal packing, simultaneously correlating these states with low-energy inherent structures. |
Wednesday, March 8, 2023 1:18PM - 1:30PM |
N16.00010: Mobile-particle clusters in supercooled liquids become increasingly noncompact as spatial dimension increases Robert S Hoy, Cory M Brown, Jack F Douglas Dynamical heterogeneity has been directly associated with mobile-particle clusters (MPCs) composed of subclusters undergoing cooperative particle exchange in the form of string-like rearrangements. These string-like clusters are of interest since their growth upon cooling closely parallels that of the hypothetical "cooperatively rearranging regions” (CRR) of Adam and Gibbs. Stevenson et al. [Nat. Phys. 2, 268 (2006)] have argued that the structure of the CRR inferred from random first order transition theory should change from fractal at high temperatures to compact at temperatures below the onset temperature for the low temperature regime of glass-formation, where relaxation and diffusion become landscape-dominated. This argument implies that if strings indeed correspond to the CRR, they should undergo a transition from a random-coil-like state to a globular compact state as temperature decreases. Our molecular-dynamics results for supercooled liquids in spatial dimensions 2 ≤ d ≤ 6, however, indicate that neither the smaller MPCs nor the strings show any tendency to become geometrically compact at low temperatures. We also generalize earlier observations by Starr et al. [J. Chem. Phys. 138, 12A541 (2013)] by finding that the geometrical structures of both MPCs and strings are consistent with dynamic clusters that self-assemble into branched and linear equilibrium polymers (with excluded volume interactions) throughout this range of d. |
Wednesday, March 8, 2023 1:30PM - 1:42PM |
N16.00011: Viscosity and elementary excitations in molecular liquids Takuya Iwashita, Bin Wu A liquid can change its shape easily and flow under stress. The flow behaviors are often characterized by the viscosity of the liquid, but the microscopic origins remain elusive. Previous studies on simple liquid metals showed that at high temperatures an elementary excitation, defined by a creation or annihilation of atomic bonds, determines the Maxwell relaxation time, that is, the viscosity divided by high frequency shear modulus. In this study, we report an extension of this concept to more complex molecular liquids, in which molecules consists of several atoms, and show similarities and differences between simple liquids and molecular liquids, including liquid silica, water, and silicon. We found that the appropriate choice of high frequency shear modulus is necesarry in estimating the Maxwell relaxation time. In addition, we discuss the role of shear modulus on structural relaxation through complex shear moduli. |
Wednesday, March 8, 2023 1:42PM - 1:54PM |
N16.00012: Entanglement in filamentous networks Yeonsu Jung, Thomas B Plumb-Reyes, Hao-Yu G Lin, L Mahadevan Packings of high aspect ratio filaments can form an effectively cohesive structure by virtue of entanglements driven by frictional and steric effects - e.g. a bird's nest. But how can we define and quantify entanglement and its role in such systems? To address this, we experimentally probe the jammed state of straight elastic rods using a combination of imaging and mechanical testing. Micro-CT scans allows us to observe the configurations in a tangled rod network with each filament resolved by image processing, and quantify their entanglement at a mesoscopic scale. This allows us to couple the geometry and topology of entanglement with the mechanical behavior of a randomly packed set of rods. |
Wednesday, March 8, 2023 1:54PM - 2:06PM |
N16.00013: Disordered Bimodal Sphere Packings Achieve Higher Packing Fractions Than Their Binary and Monomodal Counterparts Charles E Maher, Salvatore Torquato, Adam B Hopkins Studies of dense, disordered, polydisperse sphere packings are typically limited to discrete or monomodal particle-size distributions (PSD) or bimodal PSD with a very limited range of the polydispersity δ, which is the ratio of the mean and standard deviation of the PSD. Here, we use the Torquato-Jiao linear-programming packing algorithm [1] to produce strictly jammed isostatic disordered sphere packings with radius distributions given by the combination of two truncated Gaussian distributions with mean ratios α between 0.45 and 0.125 and individual-mode δ up to 0.7. We show that such bimodal packings can fill space more efficiently than their binary counterparts and equivalently polydisperse monomodal packings. Any putatively monodisperse set of particles will, in practice, exhibit a positive δ, even if small. Thus, these findings more accurately describe the packing fraction φ for practical binary (i.e., bimodal) packings and can inform the choice of PSD for tuning the density of polydisperse systems such as additive manufacturing particle beds or understanding the jamming transitions in glassy colloidal systems. Moreover, given α, one can use these results to determine which δ and relative number fraction of small spheres mimics φ of an idealized binary packing. |
Wednesday, March 8, 2023 2:06PM - 2:18PM |
N16.00014: Visualizing failure in arrested hard and sticky spheres Paddy Royall Our understanding of the mechanism by which the viscosity of supercooled liquids increases by many orders of magnitude is often described as a major challenge in condensed matter physics [1]. While understanding the static glass transition is challenging, prediction of mechanical failure of amorphous soft materials takes this to a new level and moreover has profound implications in a wide range of industrial settings, from cosmetics to argichemicals [2]. |
Wednesday, March 8, 2023 2:18PM - 2:30PM |
N16.00015: Navigating fractal canyons in glassy energy landscapes Amruthesh Thirumalaiswamy, Robert A Riggleman, John C Crocker Glass-forming systems exhibit puzzling physical and phenomenological properties, which can be directly attributed to the complex structure of their energy landscapes. In our recent study [1], we presented a modified metadynamics algorithm (MIMSE) that efficiently explores and samples low-energy regions of such high-dimensional landscapes. Further, we reported the surprising observation of canyon-like structures in such landscapes. These canyons were found to taper at lower energies and contain inherent structures (IS), that formed clusters along their floor. In this study, we use various clustering and modified dimensionality-reduction tools to study these tortuous canyons. We find strikingly similar fractal signatures for the canyons found in the landscapes of a model foam and two model glass formers - hard sphere (HS) fluids and the Kob-Andersen glass, and further, characterize them as having low effective dimensionality. For the HS glass, we use MIMSE in conjunction with systematic compression to achieve states at densities much above the jamming volume fraction, enabling us to study the canyon extremes of this landscape. Lastly, we test this algorithm on other common atomic and molecular glasses to study the presence of canyon-like structures. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700