Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session X58: Granules and GlassesFocus
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Sponsoring Units: GSOFT Chair: Wen Zhang, University of Science and Technology of China Room: BCEC 257A |
Friday, March 8, 2019 8:00AM - 8:12AM |
X58.00001: WITHDRAWN ABSTRACT
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Friday, March 8, 2019 8:12AM - 8:24AM |
X58.00002: The Jamming Energy Landscape is Hierarchical and Ultrametric Robert Dennis, Eric Corwin Recent infinite dimensional mean field results have shown that the energy landscape of glasses forms a hierarchically structured ultrametric space. We directly explore this prediction in low dimensional finite size systems. Starting in an energy minima of an over-jammed system, we apply a small random perturbation to the positions of our particles and re-minimize in order to find new minima. By enumerating these minima and calculating the distance between their force networks, we produce a small correlated portion of the overlap matrix. This matrix exhibits a clear hierarchical structure and shows the signature of an ultrametric space. That such a hierarchy exists for the jamming energy landscape provides direct evidence for the existence of a marginal phase created by the Gardner transition. |
Friday, March 8, 2019 8:24AM - 8:36AM |
X58.00003: Jammed packings behave similarly under random force and shear Peter Morse, Elisabeth Agoritsas, M. Lisa Manning, Francesco Zamponi, Eric Corwin Mean-field calculations suggest that in infinite dimensions, the response of a system to global shear and random forces may be equivalent. Whether or not this is true in 2d or 3d systems remains an open question. To address this, we develop a method for driving 2d jammed packings of disks by quasti-static persistent random forces and demonstrate that the response is similar to what is observed in athermal quasi-static shear simulations. We also investigate the gap and small force statistics in these randomly forced packings as well as the spatial organization of vibrational modes and particle rearrangements in order to compare to similar observations under shear. We expect that the results of this work may have interesting applications in understanding emergent behavior in active matter systems. |
Friday, March 8, 2019 8:36AM - 8:48AM |
X58.00004: Characteristic temperatures predicted from inherent structures Jianhua Zhang, Wen Zheng, Ning Xu We calculate the correlation and linear response to external forces for inherent structures (metastable solid states at zero temperature) of different systems. Borrowing the idea of fluctuation-dissipation relation for thermodynamically equilibrated systems, we obtain a temperature-like quantity purely from the correlation and response of inherent structures. For systems with Lennard-Johns, Weeks-Chandler-Andersen, and harmonic particle interactions, we surprisingly find that the temperature-like quantity agrees well with the crystallization or onset temperature for cystal or glass forming liquids. Our study indicates that some equilibrium information can be obtained just from nonequibrium metastable solid states, which thus proposes a novel way to calculate characteristic temperatures. Our results also suggest that effective temperatures previous calculated in ageing glasses may be simply the onset temperature of glass forming liquids. |
Friday, March 8, 2019 8:48AM - 9:00AM |
X58.00005: ABSTRACT WITHDRAWN
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Friday, March 8, 2019 9:00AM - 9:12AM |
X58.00006: Landau Theory of Complex Spherical Packing Phases Duncan McClenagan, Kai Jiang, Anchang Shi A large number of complex spherical phases, such as the Frank-Kasper phases (e.g., the σ, A15, C14 and C15 phases), have been observed in various soft matter systems. Understanding the formation of these novel ordered structures presents an interesting challenge to the soft matter community. We are developing Landau theories that are capable of describing the occurrence and stability of these phases. Our research indicates that the A15 and σ phases may emerge as stable or metastable phases in systems described by a Landau theory derived from the statistical mechanics of block copolymers. We will discuss our results and their significance to the mechanisms for the formation of complex spherical phases in soft matter systems. |
Friday, March 8, 2019 9:12AM - 9:24AM |
X58.00007: Glass Transition in Supercooled Liquids with Medium-Range Crystalline Order. Indrajit Tah, Shiladitya Sengupta, Srikanth Sastry, Chandan Dasgupta, Smarajit Karmakar The origin of the rapid dynamical slowdown in glass forming liquids in the growth of static length scales, possibly associated with identifiable structural ordering, is a much debated issue. Growth of medium range crystalline order (MRCO) has been observed in various model systems to be associated with glassy behavior. Such observations raise the question of whether molecular mechanisms for the glass transition in liquids with and without MRCO are the same. In this study we perform extensive molecular dynamics simulations of a number of glass forming liquids and show that the static and dynamic properties of glasses with MRCO are different from those of other glass forming liquids with no predominant local order. We also resolve an important issue regarding the so-called point-to-set method for determining static length scales, and demonstrate it to be a robust method for determining static correlation lengths in glass formers. |
Friday, March 8, 2019 9:24AM - 9:36AM |
X58.00008: Softening of rapidly heated nanoscale glassy films of methylbenzene Rinipal Kaur, Vladislav Sadtchenko Using Fast Scanning Calorimetry (FSC), we investigated the impact of thin film confinement on softening and vaporization of glassy films of methylbenzene in the limit of high heating rates. The glassy films of distinct thicknesses ranging from 2 to 1800 nm were grown by vapor deposition and subjected to heating with rates in excess of 105 K/s. For the films with thicknesses above 20 nm, the resulting softening kinetics strongly implied a surface facilitated mechanism: the softening originated at surfaces of a sample and progresses into its bulk via a transformation front. Yet, according to our analysis, the kinetic parameters for the softening front propagation differed significantly for the films with thicknesses below and above 300 nm. For example, the apparent activation energy barrier for the front propagation almost doubled for thicker films. We interpret these results in the framework modified Wilson-Frenkel model of softening front propagation and discuss their implications for past FSC studies of nanoscale vapor-deposited glassy films. |
Friday, March 8, 2019 9:36AM - 9:48AM |
X58.00009: Surface facilitated softening of rapidly heated glasses: recent experimental results and the fundamental mechanisms Vladislav Sadtchenko, Ulyana Cubeta, Rinipal Kaur Under certain conditions, e.g., during rapid heating, stable vapor-deposited, ordinary glassy, and even viscous liquid films can undergo softening by surface facilitated mechanism: the softening originates at the surface of a sample and progresses into its bulk via a transformation front. Despite years of research on this phenomenon, no simple theoretical model is currently available for quantitative description of glass softening by a propagating front. Based on our recent fast scanning calorimetry studies of surface facilitated glass softening and melting of superheated molecular crystals, we developed a comprehensive analytical description of the softening front propagation. This description is essentially a modification of well-established Wilson-Frenkel theory of non-equilibrium phase transitions. We present further experimental evidence in support of this analytical approach, and discuss the model’s advantages, formalism, limitations, and applicability under a variety of experimental conditions. |
Friday, March 8, 2019 9:48AM - 10:00AM |
X58.00010: Stagnant zone formation in a 2D granular bed under penetration Hongyi Xiao, Matt Harrington, Douglas Durian Penetration into a granular material is a process that is both rich in physics and important in engineering applications. Here, we present experiments with a rectangular indenter penetrating horizontally into 2D granular beds. The penetration force experienced by the indenter shows a linear increase with the penetration depth, and this force is larger for penetration into elongated particles than that into circular-shaped particles. Particle positions are tracked, and local particle-based strains are calculated, showing a triangular-shaped stagnant zone in front of the indenter, and two shear bands along the edge of the stagnant zone. A structural function, Qk, is used to characterize the local packing anisotropy, which reveals unique structural signatures as well as different structure-dynamic relations for the stagnant zone and the shear bands. The linear force law and the distinct regions observed here agree with a recent continuum model for granular penetration [1], while the structural information extracted here further demonstrates the microscopic difference between shear jammed and shear localized regions. |
Friday, March 8, 2019 10:00AM - 10:12AM |
X58.00011: Intruder spacing induces particle jamming during intrusion into granular media Swapnil Pravin, Endao Han, Heinrich M Jaeger, S. Tonia Hsieh Robotic feet often encounter granular substrates that can display complex behavior ranging from solid to fluid in a single step. The effects of foot morphology on the interaction between feet and granular substrates remain poorly understood. Inspired by the presence of toes on animal feet, the goal of this study was to characterize the effect of spacing between two intruders (“toes”) on granular material behavior. To this end, we measured and numerically simulated the force response to intrusion of two parallel square rods into dry poppy seeds while varying the rod gap spacing. Our results show that a peak in total force occurs at a gap of ~3 particle diameters, which was 20 % greater than the force at large separation (>11 particle diameters), beyond which the total produced force plateaued. We propose that this peak in force is the result of particle jamming between the intruders. To quantify the degree of particle jamming, interparticle forces were calculated from simulations. As expected, the total number of strong forces—identified as force chains—indicated greater particle jamming at gap spacings close to those corresponding to the peak force. These findings indicate that intruder separation and particle jamming can significantly affect force response to granular intrusion. |
Friday, March 8, 2019 10:12AM - 10:24AM |
X58.00012: A New Calculation of Stretched Exponential Time Dependence in As2Se3 Structural Glass Chris Nelson It has been shown by a number of authors that the relaxation times of structural glasses satisfy a stretched exponential dependence with a particular value for the exponent β at the glass temperature. Previously, this author used a free energy approach involving frustration in locally preferred structures to calculate the NQR distribution, the correct glass and Kauzzmann temperatures, as well as the spike in the heat capacity for the structural glass As2Se3. Here we calculate the correct relaxation time exponent (β=3/5) based on a statistical mechanical approach using the same approach. In addition, we show that this time dependence is entirely determined by the cooperative behavior of said structures, and at the glass transition temperature the system + bath is non-equilibrium steady state. |
Friday, March 8, 2019 10:24AM - 10:36AM |
X58.00013: Presenting New Generation Amorphous Glassy Alloys “NGAGA” Dipti Sharma, John MacDonald, Neeraj Mehta This work explores the details of “New Generation Amorphous Glassy Alloys (NGAGA)”. Several decades ago, single glassy material was explored, and one single glass transition of a single amorphous glassy material can be seen i.e. Amorphous Selenium. Later, binary glassy alloys appeared where an example of SeTe can be seen and glass transition of binary glassy alloys were explored as single but shifted glass transition. Then tertiary amorphous material came into research field i.e. SeTeAg and showed either shorter or wide and shifted kinetics of glass transition with doped material. But as time advanced, New Generation Amorphous Glassy alloys with four materials in one, appeared i.e. SeTeSnAg those brought very different results in glassy behavior. In this work, we are going to discuss changes occurred in NGAGA and in their kinetic behavior. From 1st generation to 4th generation, glassy alloys were made in our lab and studied and showed significant results in the research area of soft condensed matter and material Physics. |
Friday, March 8, 2019 10:36AM - 10:48AM |
X58.00014: Rigid clusters versus rigid regions in frictional granular packings and their role in packing mechanics J. M. Schwarz, Kuang Liu, Jonathan E Kollmer, Silke Henkes, Karen Daniels Force-chains are a well-established signature of granular packings and yet their role in packing mechanics remains elusive. We explore two new complementary mechanical signatures, namely that of rigid clusters and that of rigid regions. To determine rigid clusters, we implement a frictional version of a (3,3) pebble game on experimental packings of photoelastic disks undergoing a jamming transition. To determine rigid regions, we compute the dynamical matrix in the presence of friction and use a threshold-based criterion to determine which regions are rigid. While the rigid cluster decomposition depends on the topology of the contact network, the latter approach depends both on the topology and forces of the contact network. We find that the rigid clusters correlate well with the rigid regions, particularly near the jamming transition. We also observe "partial rigidity" with both signatures containing holes of floppiness involving groups of disks in the contact network and we look for correlations between rigid clusters/regions and force chains. In some cases we find that spanning force chains can dictate the boundary of a rigid cluster/region, while in other cases there is little correlation, hinting at the complexity of the problem. |
Friday, March 8, 2019 10:48AM - 11:00AM |
X58.00015: Granular drag induced by oblique impact Kai Huang, Valentin Dichtl, Felix Rech Considering granular medium as a complex fluid with a finite yield stress, an object moving inside has to locally unjam and mobilize the surrounding particles in order to step forward. Consequently, granular drag depends strongly on the local rheological behavior. Using a recently developed bi-static radar system capable of tracking a metallic object with a diameter down to a few millimeters, we monitor the trajectory of a projectile penetrating obliquely into a granular medium and characterize the velocity dependent granular drag in both vertical (along gravity) and horizontal directions. Recent advances in this particle tracking technique and the possibility of using it as a local rheometer for granular media will be discussed. |
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