Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session S16: Physics of Liquids III -- GlassesFocus
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Sponsoring Units: GSOFT DCP GSNP Chair: Yang Zhang, UIUC Room: 275 |
Thursday, March 16, 2017 11:15AM - 11:51AM |
S16.00001: Supercooled water: three-body interactions, IR spectra in no man's land, and the liquid-liquid critical point Invited Speaker: James Skinner No man's land is the region in the metastable phase diagram of water where it is very difficult to do experiments on liquid water because of homogeneous nucleation to the crystal. There are a number of estimates of the location in no man's land of the liquid-liquid critical point, if it exists. We suggest that published IR absorption experiments on water droplets in no man's land can provide information about the correct location. To this end, using our simulation model with explicit three-body interactions, we calculate theoretical IR spectra for liquid water over a wide range of temperatures and pressures, and use the results to argue that the temperature dependence of the experimental spectra is inconsistent with several of the estimated critical point locations, but consistent with others. [Preview Abstract] |
Thursday, March 16, 2017 11:51AM - 12:03PM |
S16.00002: Potential Energy Landscape of the Liquid-Liquid Phase Transition in Water and the transformation between Low-Density and High-Density Amorphous Ice N. Giovambattista, F. Sciortino, F. W. Starr, P. H. Poole The potential energy landscape (PEL) formalism is a valuable approach within statistical mechanics for describing supercooled liquids and glasses. We use the PEL formalism and computer simulations to study the transformation between low-density (LDL) and high-density liquid (HDL) water, and between low-density (LDA) and high-density amorphous ice (HDA). We employ the ST2 water model that exhibits a LDL-HDL first-order phase transition and a sharp LDA-HDA transformation, as observed in experiments. Our results are consistent with the view that LDA and HDA configurations are associated with two distinct regions (megabasins) of the PEL that are separated by a potential energy barrier. At higher temperature, we find that LDL configurations are located in the same megabasin as LDA, and that HDL configurations are located in the same megabasin as HDA. We show that the pressure-induced LDL-HDL and LDA-HDA transformations occur along paths that interconnect these two megabasins, but that the path followed by the liquid and the amorphous ice differ. We also study the liquid-to-ice-VII first-order phase transition. The PEL properties across this transition are qualitatively similar to the changes found during the LDA-HDA transformation, supporting the interpretation that the LDA-HDA transformation is a first-order-like phase transition between out-of-equilibrium states. [Preview Abstract] |
Thursday, March 16, 2017 12:03PM - 12:15PM |
S16.00003: Glassy dynamics in randomly pinned particle systems Anh Phan, Kenneth Schweizer We generalize the force-level, microscopic Elastically Collective Nonlinear Langevin Equation theory of activated relaxation in bulk hard sphere and thermal liquids to address the role of internal quenched disorder. So-called neutral confinement is considered where a subset of particles are randomly pinned and there is no change of equilibrium pair structure. As the pinned fraction grows, the cage scale dynamical constraints are intensified, resulting in the mobile particles becoming more localized, a larger glassy shear modulus, and an enhanced cage scale barrier. However, based on an approximate analysis of how quenched disorder modifies collective elastic field fluctuations, random pinning is predicted to effectively screen or localize the strain field associated with the longer range elastic component of the activation barrier, leading to an overall reduction of it with pinning fraction. The different response of the cage and elastic barriers to quenched disorder results in subtle predictions for how the alpha relaxation time varies with pinning fraction and system volume fraction. A semi-quantitative comparison with recent simulations of a pinned-mobile water model are consistent with the theory. Predictions are made for thermal molecular liquids. [Preview Abstract] |
Thursday, March 16, 2017 12:15PM - 12:27PM |
S16.00004: Short, intermediate and long range order in amorphous ices Fausto Martelli, Salvatore Torquato, Nicolas Giovanbattista, Roberto Car Water exhibits polyamorphism, i.e., it exists in more than one amorphous state. The most common forms of glassy water are the low-density amorphous (LDA) and the high-density amorphous (HDA) ices. LDA, the most abundant form of ice in the Universe, transforms into HDA upon isothermal compression. We model the transformation of LDA into HDA under isothermal compression with classical molecular dynamics simulations. We analyze the molecular structures with a recently introduced scalar order metric [1] to measure short and intermediate range order. In addition, we rank the structures by their degree of hyperuniformity, i.e.,the extent to which long range density fluctuations are suppressed [2]. [1] F. Martelli, H.-Y. Ko, E. C. Oguz and R. Car, \textit{A local order metric for condensed phase environments}, https://arxiv.org/abs/1609.03123 [2] S. Torquato and F. H. Stillinger, \textit{Local Density Fluctuations, Hyperuniform Systems, and Order Metrics},Physical Review E, , 041113 1-25 (2003) [Preview Abstract] |
Thursday, March 16, 2017 12:27PM - 12:39PM |
S16.00005: Breaking the glass ceiling: Configurational entropy measurements in extremely supercooled liquids Ludovic Berthier Liquids 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 {\it in-silico} configurations that have no experimental analog yet. Deploying a range of computational tools, we obtain four independent estimates of their configurational entropy. These measurements consistently indicate that the steep entropy decrease observed in experiments is found 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. [Preview Abstract] |
Thursday, March 16, 2017 12:39PM - 12:51PM |
S16.00006: Glass transition and stable glass formation of tetrachloride. Yeong Zen Chua, Mike Tylinski, S. Tatsumi, Mark D. Ediger, Christoph Schick Physical vapor deposition (PVD) has been used to prepare organic glasses with very high kinetic stability and it has been suggested that molecular anisotropy is a prerequisite for stable glass formation. Here we use PVD to prepare glasses of tetrachloromethane, a simple organic molecule with a nearly isotropic molecular structure. \textit{In situ} AC nanocalorimetry was used to characterize the vapor-deposited glasses. Glasses of high kinetic stability were produced by deposition near 0.8 $T_{\mathrm{g}}$. The isothermal transformation of the vapor-deposited glasses into the supercooled liquid state gave further evidence that tetrachloromethane forms glasses with high kinetic stability, with the transformation time exceeding the structural relaxation time of the supercooled liquid by a factor of 10$^{\mathrm{3}}$. The glass transition temperature of liquid-cooled tetrachloromethane is determined as $T_{\mathrm{g}}=$ 78 K, which is different from previously reported values. The frequency dependence of the glass transition was also determined and the fragility was estimated as $m=$ 118. The successful formation of PVD glasses of tetrachloromethane that have high kinetic stability strongly argues that molecular asymmetry is not a prerequisite for stable glass formation. [Preview Abstract] |
Thursday, March 16, 2017 12:51PM - 1:03PM |
S16.00007: Bounds on the low-temperature viscosity of a fragile glass former Vikram Jadhao, Mark Robbins One of the central debates about the nature of glass transition is whether there is a sharp phase transition where the relaxation time diverges at finite temperature or whether motion continues to gradually slow down to 0 K. Resolving this debate is challenging because of the limited range of accessible time scales. Here we use an approach based on short simulations of the nonequilibrium dynamics of a typical glass former, squalane, to calculate its equilibrium viscosity over a wide range of pressures and temperatures. The results agree with the large set of equilibrium and nonequilibrium experiments on squalane. Using this approach, we show that high-pressure, high-density simulation results set upper bounds for the rising equilibrium viscosity at ambient pressure, indicating that there is no singularity in viscosity at finite temperature. We conclude by discussing possible experimental tests of our simulation findings. [Preview Abstract] |
Thursday, March 16, 2017 1:03PM - 1:15PM |
S16.00008: Cooperative strings and glassy interfaces. Maxence Arutkin, Thomas Salez, Elie Raphael, James Forrest We present a minimal theory of glass formation based on the ideas of molecular crowding and string-like cooperative rearrangements. In the bulk case, we obtain a scaling expression for the number of particles taking part in cooperative strings as a function of density, and we recover the Adam-Gibbs description of glassy dynamics. Then, by including thermal dilatation, the Vogel-Fulcher-Tammann relation is derived. Moreover, the random and string-like characters of the cooperative rearrangements permit the prediction of a temperature-dependent expression for the cooperative length of bulk relaxation. This theoretical picture enables the exploration of the influence of sample boundaries, in various geometries where the system size becomes comparable to the bulk cooperative length, such as thin supported films and nanoparticles made of polymers. We also discuss the dependence of the glass temperature on molecular weight. [Preview Abstract] |
Thursday, March 16, 2017 1:15PM - 1:27PM |
S16.00009: Abstract Withdrawn
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Thursday, March 16, 2017 1:27PM - 1:39PM |
S16.00010: A Classical Phase Space Framework For the Description of Supercooled Liquids and an Apparent Universal Viscosity Collapse Nicholas Weingartner, Chris Pueblo, Flavio Nogueira, Kenneth Kelton, Zohar Nussinov A fundamental understanding of the phenomenology of the metastable supercooled liquid state remains elusive. Two of the most pressing questions in this field are how to describe the temperature dependence of the viscosity, and determine whether or not the dynamical behaviors are universal. To address these questions, we have devised a simple first-principles classical phase space description of supercooled liquids that (along with a complementary quantum approach) predicts a unique functional form for the viscosity which relies on only a single parameter. We tested this form for 45 liquids of all types and fragilities, and have demonstrated that it provides a statistically significant fit to all liquids. Additionally, by scaling the viscosity of all studied liquids using the single parameter, we have observed a complete collapse of the data of all 45 liquids to a single scaling curve over 16 decades, suggesting an underlying universality in the dynamics of supercooled liquids. In this talk I will outline the basic approach of our model, as well as demonstrate the quality of the model performance and collapse of the data. [Preview Abstract] |
Thursday, March 16, 2017 1:39PM - 1:51PM |
S16.00011: Preparing highly ordered glasses of discotic liquid crystalline systems by vapor deposition Ankit Gujral, Jaritza Gomez, Camille E. Bishop, Michael F. Toney, M.D. Ediger Anisotropic molecular packing, particularly in highly ordered liquid-crystalline arrangements, has the potential for optimizing performance in organic electronic and optoelectronic applications. Here we show that physical vapor deposition can be used to prepare highly organized out-of-equilibrium (glassy) solids of discotic liquid-crystalline (LC) systems. Using grazing incidence x-ray scattering, we compare 3 systems: a rectangular columnar LC, a hexagonal columnar LC and a non-liquid crystal former. The packing motifs accessible by vapor deposition are highly organized and vary from face-on to edge-on columnar arrangements depending upon substrate temperature. A subset of these structures cannot be accessed under equilibrium conditions. The structures formed at a given substrate temperature can be understood as the result of the system partially equilibrating toward the structure of the free surface of the equilibrium liquid crystal. Consistent with this view, the structures formed are independent of the substrate material. [Preview Abstract] |
Thursday, March 16, 2017 1:51PM - 2:03PM |
S16.00012: Voronoi liquids : a new model for probing glass transition Celine Ruscher, Joerg Baschnagel, Jean Farago Nowadays understanding the link between macroscopic observables and microscopic interactions among particles remains a key challenge in the physics of supercooled liquids. We developed a brand-new class of liquids for which the interactions are directly related to the inherent geometrical properties of Voronoi tessellations [1,2]. These so-called Voronoi liquids whose interactions are intrinsically many-body possess new and original microscopic properties in comparison to usual pair-potential based glass formers. These exotic features lead to non standard scaling and thermodynamic properties which can be used as new probes to investigate the different theoretical scenarios. \\ We focus here on the bidisperse Voronoi liquid tailored as to avoid crystallization. By studying this model theoretically and numerically for a wide bunch of temperatures at constant density, we observed indeed a glass transition which on the one hand displays the usual slowing down signatures common to all glass formers but also quite peculiar dynamical features, notably in the crucial mesoscopic range where unusually large relaxation times emerge. [1] J. Farago et al. EPJE, \textbf{37}, 2014 [2] C.Ruscher et al. EPL, \textbf{112}, 2015 [Preview Abstract] |
Thursday, March 16, 2017 2:03PM - 2:15PM |
S16.00013: Density Scaling of Glassy Dynamics and Dynamic Heterogeneities in Glass-forming Liquids. Yuan-Chao Hu, Yong Yang, Wei-Hua Wang The discovery of density scaling in strongly correlating systems is an important progress for understanding the dynamic behaviors of supercooled liquids. Here we found for a ternary metallic glass-forming liquid, it is not strongly correlating thermodynamically, but its average dynamics, dynamic heterogeneities and static structure are still well described by density scaling with the same scaling exponent $\gamma $. As an intrinsic material constant stemming from the fundamental interatomic interactions, $\gamma $ is theoretically predicted from the thermodynamic fluctuations of potential energy and the virial. Although $\gamma $ is conventionally understood merely from the repulsive part of the inter-particle potentials, the strong correlation between $\gamma $ and the Grüneisen parameter up to the accuracy of the Dulong-Petit approximation demonstrates the important roles of anharmonicity and attractive force of the interatomic potential in governing glass transition of metallic glass-formers. The supercooled dynamics and density scaling behaviors will also be discussed in model glass-forming liquids with tunable attractive potentials to further quantify the nonperturbative roles of attractive interactions. [Preview Abstract] |
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