Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session R53: Physics of Liquids III 
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Sponsoring Units: GSOFT DCP GSNP Chair: Issei Nakamura, Michigan Technological University Room: LACC 513 
Thursday, March 8, 2018 8:00AM  8:12AM 
R53.00001: The Grotthuss Mechanism of Aqueous Proton Diffusion is NonMarkovian Sean Fischer, Brett Dunlap, Daniel Gunlycke The structure and dynamics of aqueous protons play fundamental roles in many areas of chemistry, biology, and physics. There is a general consensus that the proton achieves its anomalously large diffusion (up to 7 times larger than similarly sized cations) through a structural exchange process, referred to as the Grotthuss mechanism, whereby protons are passed from one molecule to the next. While there has been a multitude of computational studies focused on unraveling the intricacies of proton transport, they have been biased by the assumptions made about the proton dynamics due to the lack of a robust determination of the proton diffusion coefficient from firstprinciples. Through extensive ab initio molecular dynamics simulations, we provide a thorough statistical determination of the proton diffusion coefficient. These simulations demonstrate that the standard assumption of Markovian dynamics for the Grotthuss mechanism is too simplistic. Proton transitions are correlated and result in the timescale of the Grotthuss mechanism being substantially shorter than was previously thought, no matter the structure that the aqueous proton adopts. 
Thursday, March 8, 2018 8:12AM  8:24AM 
R53.00002: Phonon Assisted Unipolar and Bipolar Trappy Protonic Transport in Pure Water on Melted Ice Lattice Bin Jie, ChihTang Sah Melted ice lattice of the hexagonal close packed (HCP) primitive unit cell containing four water molecules in each cell, based on the 1933 Bernal and Fowler structure, was convincingly proven by the 1935 Linus Pauling residual entropy theory. It was used by us to model the electrical mobility of pointmass protons in pure liquid water, giving two alternative models: (1) the bipolar proton and prohol (protonhole) model, which is the counterpart of the electron and hole model in the electronic semiconductor, such as element semiconductor Silicon crystal; (2) the unipolar threepositive pointmass proton trapping model. Proton trapping and detrapping at each dynamic protonic trapping center are assisted by one protonic phonon absorption and emission, characterized by an experimental activation energy. From the experimental data vs temperature of the three properties, ion product and two ion mobilities, three thermal activation energies were obtained using our physics based algorithm. Using the onedimension springmass vibration model, the ratios of the thermal energies are consistent with those from the four water molecules in the HCP primitive unit cell, and the energies match the vibration frequencies of isolated water molecule in vapor. 
Thursday, March 8, 2018 8:24AM  8:36AM 
R53.00003: Capillarycondensationinduced stress in complex multiscale porous materials Edmond Zhou, Katerina Ioannidou, Enrico Masoero, Mohammad Mirzadeh, Martin Bazant, Roland Pellenq The adsorption/desorption isotherms in porous media is a powerful and widely 
Thursday, March 8, 2018 8:36AM  8:48AM 
R53.00004: Simulation of Tracer Particle Diffusion in Attractive and Repulsive Glassy Matrices Ryan Roberts, Ryan PolingSkutvik, Jacinta Conrad, Jeremy Palmer Anomalous transport in confined systems is most commonly associated with particle subdiffusion. Characterization of confined particle dynamics has been extended to matrices of different topologies, including ordered and disordered particles; the effects of slow relaxations of the confining matrix, however, have received comparatively little attention. We use eventdriven molecular dynamics to scrutinize the diffusion of tracer particles confined within ”attractive” and “repulsive” glassy matrices, which are dominated by different relaxation dynamics and mechanisms, formed from a wellcharacterized, bidisperse system of colloidal spheres with hard cores. These distinct relaxation processes strongly influence the dynamics and trajectories of the tracer particles. By varying the size of the tracer relative to that of a matrix particle, we investigate the role of size asymmetry on tracer dynamics. Because dispersing particles within slowlyrelaxing matrices with varying interactions appear in settings ranging from the crowded cytoplasm inside cells to natural soils in the environment to artificial nanocomposites, these results provide insight into coupling between particle transport and matrix dynamics across a range of scientifically and technologically relevant processes. 
Thursday, March 8, 2018 8:48AM  9:00AM 
R53.00005: Picosecond Dynamics of Propylene Carbonate Investigated using Ultrafast Optical Kerr Effect Spectroscopy John Bender, Marcus Cicerone Ultrafast optical Kerr effect (OKE) spectroscopy is used to investigate the picosecond timescale dynamics of propylene carbonate. The liquid is studied over a wide range of temperatures ranging from the deeply supercooled state through well above the melting temperature. These dynamics exhibit complex, nondiffusive behavior and are shown to be heterogeneous in nature. A simple twostate model is presented to describe the dynamics in relation to the local structure of the liquid, where a fast relaxation mechanism is associated with molecules in tightly caged configurations, whereas the slower mechanism is associated with loosely caged domains within the liquid. 
Thursday, March 8, 2018 9:00AM  9:12AM 
R53.00006: Thermal Jamming in Supercooled Liquids Dillon Sanders, Jacob Eapen We propose that supercooled liquids can quantitatively be described in terms of thermally jammed states. Our proposition rests on the wellknown approach of partitioning a liquid state into a superposition of harmonic oscillators and hard spheres (HS). The fraction f_{HS} of atoms that comprise the HS partition governs the equivalent packing fraction φ of the hard sphere partition. We postulate that f_{HS} is inversely proportional to the radial distribution function’s value at the closest contact point for hard spheres, which can be connected to HS diffusion through Enskog’s theory. Using atomistic simulations of three model supercooled liquids, and using an appropriate equation of state for the metastable fluid branch of HS, we show that φ approaches the randomclosepacked limit of ~0.64 (φ_{c}) for all three systems when the temperature is sufficiently lowered. Interestingly, we observe a powerlaw variation of the diffusion coefficients and f_{HS} with φ_{c}  φ that is universal for the three model systems. This universality compels us to view the dynamic slowing down as a property of the system. The vanishingly small f_{HS} in the limit φ → φ_{c} suggests an intriguing possibility of describing the glass transition as a consequence of thermal jamming. 
Thursday, March 8, 2018 9:12AM  9:24AM 
R53.00007: Solvation in SpaceTime: PreTransition Effects in Trajectory Space Shachi Katira, Juan Garrahan, Kranthi Mandadapu We demonstrate pretransition effects in spacetime in trajectories of systems in which the dynamics displays a firstorder phase transition between distinct dynamical phases. These effects are analogous to those observed for thermodynamic firstorder phase transitions, most notably the hydrophobic effect in water. Considering the East model as an example, we study the properties of spacetime 'solvation' by examining trajectories where finite spacetime regions are conditioned to be inactive in an otherwise active phase. We find that solvating an inactive region of spacetime within an active trajectory shows two regimes in the dynamical equivalent of solvation free energy: an 'entropic' small solute regime in which uncorrelated fluctuations are sufficient to evacuate activity from the solute, and an 'energetic' large solute regime that involves formation of a soluteinduced inactive domain with an associated activeinactive interface bearing a dynamical interfacial tension. As a result of this dynamical tension there is a dynamical analog of the hydrophobic collapse that drives the assembly of large hydrophobes in water. We discuss the general relevance of these results to properties of dynamical fluctuations in systems with slow collective relaxation such as glass formers. 
Thursday, March 8, 2018 9:24AM  9:36AM 
R53.00008: Effect of Attractive Forces on the Slow Dynamics of Colloidal Suspensions and Supercooled Liquids Ashesh Ghosh, Kenneth Schweizer The role of attractive interactions on emergent glass and gellike dynamics in thermal liquids and colloidal suspensions is of wide interest. Existing microscopic theories based on local cage scale physics where dynamical constraints enter only via the structural pair correlations have not been able to explain a number of aspects of activated dynamics in dense attractive fluids. We construct a microscopic theory based on real forces and pair structure for these systems within the framework of the Elastically Collective Nonlinear Langevin Equation approach which treats structural relaxation as a coupled localnonlocal event involving cage scale large amplitude hopping and longer range facilitating elastic fluctuation. The influence of the functional form and spatial range of the interparticle attraction on activated relaxation, glass melting, and attractive glass and dense gel formation have been analyzed. Various dynamical features are shown to be strongly dependent upon the precise form of the microscopic forces (e.g., LJ versus exponential attractions), including dynamical reentrancy. 
Thursday, March 8, 2018 9:36AM  9:48AM 
R53.00009: Electrowetting Assisted Selective Printing of Liquid Metals Alexander Watson, Alexander Cook, Christopher Tabor 
(Author Not Attending)

R53.00010: Abstract Withdrawn In this study we use particle tracking to quantitatively examine crystallization in a Quasi2D granular fluid. Recent theoretical studies have observed that the addition of relatively small concentrations of impurities to a monodisperse hard sphere fluid radically alters the nature of the phase behaviour. Motivated by this we investigate experimentally the nature of the crystallization observed when key parameters are varied. We find differences in the phase behaviour with changes in particle elasticity and also with the addition of impurities. 
Thursday, March 8, 2018 10:00AM  10:12AM 
R53.00011: Entropic, Electrostatic, and Interfacial Model for Osmotic Pressure and Shear Moduli of Concentrated Disordered Charged Droplets Ha Seong Kim, Frank Scheffold, Thomas Mason We present a free energy model describing the osmotic pressure Π and the linear plateau shear moduli G'_{p} of disordered chargestabilized uniform emulsions for droplet volume fractions φ below, near, and above the jamming point. The three principle contributing free energy terms arise from entropy, screenedcharge electrostatic interactions, and interfacial droplet deformations (EEI). We numerically evaluate Π(φ) and G'_{p}(φ) by minimizing the total free energy with respect to a common average deformation parameter which links all three terms and taking the appropriate thermodynamic derivative. We demonstrate that this EEI model fits measurements of Π(φ) and G'_{p}(φ) for quenched disordered nano and microscale monodisperse chargestabilized emulsions, including those having added concentrations of NaCl. In addition, trends in optical measurements of longtime plateau mean square displacements of monodisperse chargestabilized emulsions having varying φ and concentrations of NaCl can match the trends in lowfrequency G'_{p}(φ) predicted by this EEI model. This EEI model may serve as a good starting point for understanding other disordered systems of chargestabilized uniform spherical soft colloidal objects. 
Thursday, March 8, 2018 10:12AM  10:24AM 
R53.00012: Microscopic Rearrangements in the Flow of Highly Polydisperse Jammed Emulsions Yonglun Jiang, Carlos Orellana, Eric Weeks We study the flow of dense polydisperse quasitwodimensional emulsions. In particular, we are interested in highly polydisperse samples with the largest droplets as much as ten times the size of the smallest. The droplets are confined between two parallel glass plates so that the system is quasi2D. A flow is driven with a syringe pump. We use video microscopy to examine local rearrangements as the sample flows and we study how rearrangements differ for large and small droplets. In particular, we find the large droplets follow the mean flow, while the small droplets have significant nonaffine motions and move more erratically. We quantify these results using nearest neighbor changes as well as D^{2}_{min} (Falk & Langer, PRE 1998). 
Thursday, March 8, 2018 10:24AM  10:36AM 
R53.00013: Probing the CrystaltoGlass Transition using the Mechanical Properties of 2D Clusters of Droplets JeanChristophe OnoditBiot, Pierre Soulard, Solomon Barkley, Eric Weeks, Thomas Salez, Elie Raphael, Kari DalnokiVeress Lightly attractive stabilized oil droplets (R approximately 10 microns), suspended in an aqueous solution, are used to prepare model quasi2D aggregates (tens of droplets). We investigate the response of the clusters ranging from a perfectly ordered crystal (monodisperse aggregate) to a disordered glass (bidisperse aggregate). Disorder in the system is continuously varied by mixing two monodisperse populations of droplets in different proportions. The mechanical properties of the clusters are assessed by compressing the aggregates between two parallel boundaries, one of which acts as a force sensor. The forces acting on the aggregate are directly measured and correlated with the internal rearrangements observed by optical microscopy. The force measurement reveals a signature of the cluster composition and provides insight into the crystaltoglass transition. We find that introducing even a small amount of disorder in the clusters has a strong impact on the measured yield stress. Finally, a statistical model fully supports our experimental results. 
Thursday, March 8, 2018 10:36AM  10:48AM 
R53.00014: Holographic Monitoring of Coarsening in Binary OilinWater Emulsions Mark Hannel II, Carla Salguero, Fook Cheong, David Ruffner, Priya Kasimbeg, Jaroslaw Blusewicz, Laura Philips, David Grier We use holographic characterization to monitor changes in the diameters and compositions of individual emulsion droplets during coarsening of binary emulsions. When the initial droplets are composed of two distinct but miscible fluids, the increase in droplet size is accompanied by compositional mixing, with the end result being a homogeneous emulsion of stoichiometrically mixed droplets. Holographic characterization can distinguish Ostwald ripening from coarsening dominated by collisional coalescence. Our measurements reveal that model oilinwater emulsions composed of slightly soluble aromatic oils coarsen almost exclusively through ripening. Insoluble silicone oil emulsions, by contrast, are kinetically stable, but can be made to coalesce by mixing or sonication. The ability to track both size and composition provides insights into the aging process in heterogeneous emulsion that cannot be obtained in other ways. 
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