Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session M26: Disordered and Glassy Systems |
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Sponsoring Units: DSOFT Chair: John Crocker, University of Pennsylvania Room: 403 |
Wednesday, March 4, 2020 11:15AM - 11:27AM |
M26.00001: Linking Melt Dynamics with Glass Topological Phases in GexPxSe100-2x Ternary Aaron Welton, Ralph Chbeir, Soumendu Chakravarty, Punit Boolchand We have synthesized homogeneous equimolar GexPxSe100-2x ternary glasses over a wide range of compositions 0< x< 26%. 1.5 gram sized samples in evacuated (5mm ID) quartz tube were alloyed at 960 oC for 10 days. When Raman spectra taken along the 1 inch long melt column became identical the samples were declared to be homogenous. Homogeneity means the variance of Se along the melt column decreased to ~0.1%. Modulated DSC experiments were undertaken and trends in Tg(x), del Cp(x) and the enthalpy of relaxation at Tg, del Hnr(x), were established. We observe a reversibility window in the 9%<x<18% range fixing the three topological phases; flexible phase 0<x<9%, intermediate phase (IP) 9%<x<18% , stressed-rigid phase 18%<x<26%. The IP of this ternary is the widest of any chalcogenide multicomponent chalcogenide glass system, a feature that could be tied to the existence of the Ethylene like P2Se(1/2)4 local structure besides the QT, Se=P(Se1/2)3 and PYR P(Se1/2)3 ones. Molar volumes reveal a volumetric window with Vm(x) decreasing in the IP range from the average behavior across all x. Melt fragility index, m(x), measurements show a Gaussian like minimum near m=15 in the center of the IP and increasing to m(x)>20, both in the flexible (x<9%) and stress-rigid (x>18%) |
Wednesday, March 4, 2020 11:27AM - 11:39AM |
M26.00002: Local and Extended range molecular structures of (Na2O)x(P2O5)100-x glasses probed by Raman Scattering and Infrared reflectance Vamshi Kiran Gogi, Avik Mandal, Chandi Mohanty, Ralph Chbeir, Punit Boolchand Raman scattering and IR reflectance reveal striking similarities between crystalline (c-) and glassy (g-) NaPO3. The c- and g- are each composed largely of chains of Q2 species, a 4-fold P having 2 bridging (Ob) and 2 terminal (Ot) Oxygen neighbors, and display three vibrational features; an asymmetric stretch (as) of P-Ot (1300 cm-1), a symmetric stretch (ss) of P-Ot (1172 cm-1) and a ss of P-Ob (685 cm-1). There are glaring differences as well, and these come from the fact that ss of P-Ot and P-Ob although quite narrow in the c- but are rather broad in the g-, and can be deconvoluted in terms of a triad of modes due to long chains (LC), large rings (LR) and small rings (SR) in the latter. These triad of modes are also observed in IR displaying complementary behavior, with modes of SR and LR, weakly excited in Raman but strongly in IR. These vibrational features are also observed at non-stoichiometric (x ≠ 50%) compositions ranging from 20%<x<61% and have permitted to elucidate the role of glass structure in stabilizing the three Topological phases. In the Intermediate Phase range1 (37.5% < x < 46%), LC far exceed the count of LR and SR thus promoting the configurational entropy of that phase. |
Wednesday, March 4, 2020 11:39AM - 11:51AM |
M26.00003: Molecular origin of the 7-folds narrowing of the Tg transition upon aging in Se-rich multicomponent glasses Ralph Chbeir, Shreeram J Dash, Punit Boolchand The nature of the glass transition temperature in Se-rich (x < 4%) ternary GexAsxSe100-2x [1] glasses is examined as a function of room temperature aging in Modulated DSC experiments. Our experiments show Tg(x) to increase by 6°C with x displaying a trapezoidal variation in the 0% < x < 4% range, with the enthalpy of relaxation, ΔHnr increasing 4-folds and the width (W) of the glass transition decreasing 7-folds upon RT aging for 8 months. The molecular origin of these changes can be connected with the polymeric Sen chains in the fresh glass steadily correlating with each other to become quasi-helical provided n > 8. These features are due to the undercoordinated nature of Se glass rendering compositions x < xc to be super-flexible when the length of chains exceeds 10 atoms. Parallel results were obtained in the GexSe100-x [1] binary, underscoring that these effects are strictly controlled by the topology or network connectedness. |
Wednesday, March 4, 2020 11:51AM - 12:03PM |
M26.00004: Origin of the Raman active 490 cm-1 mode in binary As-S and Ge-S and ternary Ge-As-S glasses from compositional studies and Ab-initio Cluster calculations. Soumendu Chakravarty, Ralph Chbeir, Badriah Almutairi, Shibalik Chakraborty, Koblar Jackson, Punit Boolchand Raman scattering results on binary As-S and Ge-S and ternary Ge-As-S provide evidence of a mode near 490 cm-1. The fractional scattering strength of the mode in question normalized to the sum of the S8 (472cm-1) and Sn chain (461cm-1) mode reveals evidence of a local maximum near x = 25% in binary AsxS100-x glasses and near y = 20% in binary GeyS100-y glasses. These results are most suggestive that the mode in question has a frequency which is tied to the S-S stretch between a pair of AsS3 pyramids or between a pair of GeS4 tetrahedra. We have now carried forward NRLMOL calculations on select clusters and results of these will be compared to experiments. Preliminary results place the symmetric stretch mode frequency at 450 cm-1 for a 14 atom cluster of (H-S-As)2 -S-S- (As-S-H)2. |
Wednesday, March 4, 2020 12:03PM - 12:15PM |
M26.00005: Compositional variation of the Specific Heat Cp(x) in binary GexSe100-x melts and glasses across the Intermediate Phase. Matthew Burger, Ralph Chbeir, Bernard Goodman, Punit Boolchand We have examined the specific Heat Cp in the glassy state and the metastable liquid state across Tg in binary GexSe100-x system in the 19% < x < 26% range of compositions focusing on the Intermediate Phase. The bulk glasses used in the present Modulated DSC study were the ones synthesized by Bhosle et al.1. Our results show Cp(glass) and Cp(liquid), each term to display a broad Gaussian-like maximum centered about the mid -point composition, x = 23%, of the Intermediate Phase. We are also investigating the variation of Cp(liquid) at higher temperature in the Tg < T < 550°C range to look at any anomalies that could be related to the liquid-liquid transition recently suggested2. |
Wednesday, March 4, 2020 12:15PM - 12:27PM |
M26.00006: Universal hidden order in amorphous cellular geometries Gerd Schroeder-Turk Partitioning space into cells with certain extreme geometrical properties is a central problem in many fields of science and technology. Here we investigate the Quantizer problem, defined as the optimisation of the moment of inertia of Voronoi cells, i.e., similarly-sized ‘sphere-like’ polyhedra that tile space are preferred. We employ Lloyd’s centroidal Voronoi diagram algorithm to solve this problem and find that it converges to disordered states associated with deep local minima. These states are universal in the sense that their structure factors are characterised by a complete independence of a wide class of initial conditions they evolved from. They moreover exhibit an anomalous suppression of long-wavelength density fluctuations and quickly become effectively hyperuniform. Our findings warrant the search for novel amorphous hyperuniform phases and cellular materials with unique physical properties. This research was published in M.A. Klatt et al, Nature Communications 10, 811 (2019). |
Wednesday, March 4, 2020 12:27PM - 12:39PM |
M26.00007: Bulk-Boundary Correspondence In Soft Matter : From Fractals to Order Parameter Mehmet Ramazanoglu, Sener Özönder, Rumeysa Salci
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Wednesday, March 4, 2020 12:39PM - 12:51PM |
M26.00008: Micro-phase separation breaks hyperuniformity of jammed solids Ding Xu, Qinyi Liao, Ning Xu Maximally random jammed (MRJ) packings of hard spheres are conjectured to be hyperuniform. When density increases away from the MRJ point, it was found that the randomly jammed states gradually lose the hyperuniformity. A possible explanation is the growth of the structural order, i.e., the system becomes the mixture of order and disorder phases when density increases. However, it remains unclear whether this is the case in polydisperse systems. To clarify the picture, we numerically study polydisperse jammed states in two dimensions by quickly compressing supercooled hard disk liquids from different densities and by quickly quenching high temperature states of soft particles with repulsions. Upon the increase of density, we find a tendency of micro-phase separation (MPS) in both types of systems. In the presence of MPS, the spectral density χ(q) of dense packings of hard disks becomes flater and keeps decreasing in the q→0 limit, distinct from those with conventional phase separations. Furthermore, by comparing the results with soft particle states with similar degrees of MPS, we find that the MPS is responsible for the flattening of χ(q) in the q→0 limit. |
Wednesday, March 4, 2020 12:51PM - 1:03PM |
M26.00009: The role of hydrodynamic interactions on the long-time structural fate of dense colloidal suspensions Monica E. A. Zakhari, Jialun Wang, Gaddiel Ouaknin, Roseanna Zia The colloidal glass transition presents an intriguing temporal convolution of structural, dynamical, and mechanical effects during aging. This competition simultaneously advances aging and deepens arrest. In this work, we study the mechanics of this competition by considering both the equilibrium and non-equilibrium solidification processes, i.e. crystallization and vitrification, respectively, utilizing large-scale Stokesian dynamic simulations that are massively parallelized. Jumps from liquid into the solid region are executed via controlled volume-fraction quenches, where the speed of the quench is used to modulate the particle dynamics and, consequently, permits toggling between equilibrium and arrested states. We find that the long-time structural fate of the suspension, i.e. a glass or a crystal, is determined during the quench itself and is mechanistically regulated by many-body hydrodynamic interactions. |
Wednesday, March 4, 2020 1:03PM - 1:15PM |
M26.00010: Why phonon scattering in glasses is universally small at low temperatures Herve M. Carruzzo, Clare Yu We present a novel view of the standard model of tunneling two level systems (TLS) to explain the puzzling universal value of a quantity, C ~ 3 x 10-4, that characterizes phonon scattering in glasses below 1 K as reflected in thermal conductivity, ultrasonic attenuation, internal friction, and the change in sound velocity. Physical considerations lead to a broad distribution of phonon-TLS couplings that (1) exponentially renormalize tunneling matrix elements, and (2) reduce the TLS density of states through TLS-TLS interactions. We find good agreement between theory and experiment for a variety of individual glasses. |
Wednesday, March 4, 2020 1:15PM - 1:27PM |
M26.00011: Nearest Neighbor Functions for Stealthy Hyperuniform Many-particle Ground States Timothy Middlemas, Salvatore Torquato We present new analytical theories backed by simulation for the nearest neighbor functions of disordered stealthy hyperuniform many-particle ground states. Stealthy systems display a variety of ordered and disordered phases, and have been related to novel photonic band gaps in disordered systems. They can also be shown to have optimal transport properties, such as the fluid permeability, trapping constant, and elastic properties. The nearest neighbor functions, which include the probability to find a hole of a certain radius, are intrinsically related to the geometric properties of stealthy systems, such as their bounded hole size and quantizer error. The manner in which these functions approach the critical (bounded) hole size is a fundamental geometrical question (in particular, whether they behave like ordered lattices), and is also related to their thermodynamics. We use insights from simulation and previous analytical work to develop new analytical theories of the core and tail regions of these functions, and comment on their implications for geometric problems and material properties. |
Wednesday, March 4, 2020 1:27PM - 1:39PM |
M26.00012: Analytical theory of enhanced logarithmic Rayleigh scattering in amorphous solids Bingyu Cui, Alessio Zaccone The damping or attenuation coefficient of sound waves in solids due to impurities scales with the wavevector to the fourth power, also known as Rayleigh scattering. In amorphous solids, Rayleigh scattering may be enhanced by a logarithmic factor although computer simulations offer conflicting conclusions regarding this enhancement and its microscopic origin. With tensorial replica field strategy, a theoretic derivation based on heterogeneous elasticity suggests that the logarithmic enhancement to Rayleigh scattering of phonons might be ascribed to long-range (power-law) power law decay in spatial elastic disorder in amorphous solids. Further, the density of states (DOS) associated with self-consistent equations of self-energy in the model exhibit power d+1 decay in low frequency regime, supporting the evidence of numerical simulation in sound waves. |
Wednesday, March 4, 2020 1:39PM - 1:51PM |
M26.00013: Tracer Transport in Attractive and Repulsive Supercooled Liquids and Glasses Ryan C Roberts, Jacinta Conrad, Jeremy Palmer The transport of small penetrants through disordered materials with glassy dynamics is encountered in drug delivery and chemical separations. Understanding the influence of matrix structure and fluctuations on penetrant motions remains a challenge. We use event-driven molecular dynamics to investigate the transport of small, hard-sphere tracers in matrices of square-well particles. Short-range attractions between matrix particles give rise to reentrant dynamics in the supercooled regime, in which the liquid's relaxation time increases dramatically upon heating or cooling. Heating results in a repulsive supercooled liquid where relaxations are frustrated by steric interactions between particles, whereas cooling produces an attractive liquid in which relaxations are hindered by long-lived interparticle bonds. Further cooling/heating, or compression, of the supercooled liquids results in the formation of distinct glasses. Our study reveals that tracer transport in these liquids and glasses is influenced by matrix structure and dynamics. The relative importance of each factor varies between matrices and is examined by analyzing mean-square displacements, caging behavior, and trajectories sampled from the isoconfigurational ensemble. |
Wednesday, March 4, 2020 1:51PM - 2:03PM |
M26.00014: Glass Transition in Supercooled Liquids with Medium-Range Crystalline Order Indrajit Tah, Shiladitya Sengupta, Chandan Dasgupta, Srikanth Sastry, 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. |
Wednesday, March 4, 2020 2:03PM - 2:15PM |
M26.00015: Understanding how the degree of disorder affects structural colors of colloidal packings Ming Xiao, Anna B. Stephenson, Victoria Hwang, Vinothan Manoharan Disordered structures that multiply scatter light sometimes show phenomena such as Anderson localization, structural colors, and super whiteness. We investigate the scattering from dense packings of spherical colloidal particles in a weak multiple scattering region. Using a Monte Carlo framework, we predict the wavelength-dependent reflectance (colors) of simulated packings. To quantify the degree of disorder, we calculate the structure factor. We then explore how variations in the structure factor affect both the reflectance and the angle-dependence of the colors. We find only the first peak of the structure factor determines the feature of the reflectance, which provide guidance to control colloidal packings to tune the colors. |
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