Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session A3: Physics of Liquids I -- Multicomponent Liquids and Solvation |
Hide Abstracts |
Sponsoring Units: GSOFT GSNP DCP Chair: Justin Burton, Emory University Room: 262 |
Monday, March 13, 2017 8:00AM - 8:12AM |
A3.00001: Population Annealing Simulations of Binary Hard Sphere Mixtures Jared Callaham, Jonathan Machta Population annealing is a sequential Monte Carlo algorithm that has proven successful in studying spin glass systems. In this talk I describe its application to a binary mixture of hard spheres. A large population of replicas of the system are simulated in parallel using Event Chain Monte Carlo and as the population is gradually compressed, the replicas are randomly resampled to preserve the equilibrium hard sphere distribution. Population annealing provides a direct estimate of the entropy of the system as a function of packing fraction. Using population annealing, we are able to maintain equilibrium into the high density glassy regime and accurately measure the equation of state and its deviations from the BMCSL equation of state. For even higher packing fractions, equilibration is lost but population annealing serves as a useful jamming protocol. We conclude that population annealing is an effective tool for studying equilibrium glassy fluids and the jamming transition. [Preview Abstract] |
Monday, March 13, 2017 8:12AM - 8:24AM |
A3.00002: Identifying Symmetries via Machine Learning Rashi Verma Nucleation is the non-equilibrium process by which a metastable phase transforms to a stable one. For example, in liquid-to-solid nucleation, fluctuations in a supercooled liquid eventually give rise to nucleating droplets, which may continue to grow to the stable crystalline phase. Surprisingly, the nucleating droplets often exhibit atomic symmetries very different than that of the stable phase. Here, we develop a fundamentally new way to think about the nucleation process, and to study precursor fluctuations that may exist in the metastable phase. [Preview Abstract] |
Monday, March 13, 2017 8:24AM - 8:36AM |
A3.00003: Anomalous sound absorption in the Voronoi liquid Jean Farago, Céline Ruscher, Alexandr Semenov, Joerg Baschnagel The physics of simple fluids in the hydrodynamic limit, and notably the connection between the proper microscopic scales and the macroscopic hydrodynamical description are nowadays well understood. In particular, the three peak shape of the dynamical structure factor $S(k,\omega)$ is a universal feature, as well as the $k$-dependence of the peak position ($\propto k$), and width $\propto k^2$, the latter accounting for the sound attenuation rate. In this talk, I will present a theoretical model of monodisperse fluid, whose interactions are defined via the Voronoi tessellations of the configurations (called the Voronoi liquid and first studied in C. Ruscher et al., {\em Europhys. Lett.}, {\bf 112}, 66003 (2015) ), which displays at low temperatures a marked violation of the universal features of $S(k,\omega)$ with sound attenuation rate only $\propto k$. This anomalous behaviour, which apparently violates the basic symmetries of the liquid state, is traced back to the existence of a timescale which is both (1) short enough for the viscoelastic features of the liquid to impact the relaxational dynamics and (2) long enough for the momentum diffusion to be substantially slower than the sound propagation on that characteristic time. [Preview Abstract] |
Monday, March 13, 2017 8:36AM - 8:48AM |
A3.00004: Non-classical nucleation theory in colloidal fluids: Kinetically persistent precursors M.A. Duran-Olivencia, P. Yatsyshin, J.F. Lutsko, S. Kalliadasis In recent years, a flurry of experimental observations has suggested that most phase transitions occur in a multistage manner, via intermediate phases. These precursors to the final phase are generally understood as the local minima of the free energy of the system. Inherently, the classical paradigm of nucleation has no capacity to describe neither the origin nor the role played by these precursors in the nucleation pathway. In this work, we present a systematic theoretical framework capable of describing the precursor phases in a self-consistent way. We demonstrate that nucleation precursors can appear even in situations involving a single free-energy barrier. This contradicts previous phenomenological approaches, which always characterise intermediate phases as the minima of a complex free-energy landscape. We show that a kinetically-induced mechanism temporarily stabilizes an intermediate phase, which thus is not the result of a local minimum of the free energy but results from the entropic cost of cluster formation. Moreover, the appearance of precursors does not seem to influence the overall nucleation time, which is governed by the free-energy barrier. The mechanism uncovered in this study can be used to explain recently reported experimental findings in crystallization. [Preview Abstract] |
Monday, March 13, 2017 8:48AM - 9:00AM |
A3.00005: Polyamorphism in Tetrahedral Liquids Jeremy Palmer Tetrahedral liquids exhibit well-known thermophysical anomalies that arise from a competition between high-density and low-density local coordination structures in the fluid. These structures allow such systems to form both high-density and low-density glassy phases upon rapid cooling. It has been posited that these experimentally observed glass phases are associated with two distinct ergodic liquids at higher temperatures that undergo a first-order liquid-liquid phase transition (LLPT). Direct experimental observation of these hypothesized LLPTs, however, has proved to be challenging because they are typically predicted to occur at conditions where the liquids are metastable with respect to crystallization. Here, we discuss recent computational studies of model tetrahedral liquids that exhibit metastable LLPTs. Using free energy analysis, we show that the ST2 water model, the TIP5P water model, and an ionic model of silica exhibit LLPTs under deeply supercooled conditions. We investigate the nature of the LLPTs in these systems and show that liquid-liquid phase separation can be observed in large-scale molecular dynamics simulations. Finally, we investigate nucleation of the stable crystal phase and demonstrate that this process is distinct from those involved in LLPTs. [Preview Abstract] |
Monday, March 13, 2017 9:00AM - 9:12AM |
A3.00006: A closure relation to molecular theory of solvation for macromolecules Alexander E. Kobryn We propose a closure to the integral equations of molecular theory of solvation, particularly suitable for polar and charged macromolecules in electrolyte solution. This includes such systems as oligomeric polyelectrolytes at a finite concentration in aqueous and various non-aqueous solutions, as well as drug-like compounds in solution. The new closure (KGK closure) imposes the mean spherical approximation (MSA) almost everywhere in the solvation shell but levels out the density distribution function to zero inside the repulsive core and in the spatial regions of strong density depletion emerging due to molecular associative interactions. We test the performance of the KGK closure coupled to the reference interaction site model (RISM) on the examples of LJ liquids, polar and nonpolar molecular solvents, including water, and aqueous solutions of simple ions, and use the KGK closure to obtain the solvation structure and thermodynamics of oligomeric polyelectrolytes and drug-like compounds at a finite concentration in electrolyte solution, for which no convergence is obtained with other closures. We further test the 3D-version of the KGK closure with 3D-RISM for molecular mixtures as well as oligomeric polyelectrolytes and drug-like molecules in electrolyte solutions. [Preview Abstract] |
Monday, March 13, 2017 9:12AM - 9:24AM |
A3.00007: Stiffening of Dilute Alcohol and Alkane Mixtures with Water Hank Ashbaugh We probe the anomalous compressibilities of dilute mixtures of alcohols and alkane gases in water using molecular simulations. The response to increasing solute concentration depends sensitively on temperature, with the compressibility decreasing upon solute addition at low temperatures and increasing at elevated temperatures. The thermodynamic origin of stiffening is directly tied to the solute's partial compressibility, which is negative at low temperatures and rises above water's compressibility with increasing temperature. Hydration shell waters concurrently tilt towards clathrate-like structures at low temperatures that fade with heating. Kirkwood-Buff theory traces the solute's partial compressibility to changes in the solute-water association volume upon heating and incongruous packing of waters at the boundary between the more structured hydration shell and bulk water. [Preview Abstract] |
Monday, March 13, 2017 9:24AM - 9:36AM |
A3.00008: What Can Interfacial Water Molecules Tell Us About Solute Structure? Adam Willard The molecular structure of bulk liquid water reflects a molecular tendency to engage in tetrahedrally coordinated hydrogen bonding. At a solute interface water’s preferred three-dimensional hydrogen bonding network must conform to a locally anisotropy interfacial environment. Interfacial water molecules adopt configurations that balance water-solute and water-water interactions. The arrangements of interfacial water molecules, therefore encode information about the effective solute-water interactions. This solute-specific information is difficult to extract, however, because interfacial structure also reflects water’s collective response to an anisotropic hydrogen bonding environment. Here I present a methodology for characterizing the molecular-level structure of liquid water interface from simulation data. This method can be used to explore water’s static and/or dynamic response to a wide range of chemically and topologically heterogeneous solutes such as proteins. [Preview Abstract] |
Monday, March 13, 2017 9:36AM - 9:48AM |
A3.00009: Water in Protein Crystals Irem Altan, Diana Fusco, Pavel Afonine, Patrick Charbonneau Water is both the solvent and an active component of biological processes. Protein crystals contain up to $80\%$ water by volume. Yet water-protein interactions are challenging to probe by X-ray diffraction because of the probabilistic nature of solvation, the mosaic of hydrophilic and hydrophobic residues on the protein surface, and the complexity of the protein surface. We compare the solvent structure obtained from diffraction data for which experimental phasing is available to that obtained from constrained molecular dynamics (MD) simulations. The resulting spatial density maps show that MD water models capture the radial extent of biomolecular solvation fairly well, irrespective of the choice of MD water, but cannot reproduce the real space distribution of solvent with a comparable accuracy. MD simulations can predict only a fraction of the assigned crystal waters. These differences are due to shortcomings of both the water models and the protein force fields. Our findings nonetheless suggest that MD-derived densities can be utilized to infer the protonation states of side chains, provided that they are sufficiently solvent-exposed. Our work also paves the way to treating water’s contribution to protein refinement more accurately through the development of hybrid models. [Preview Abstract] |
Monday, March 13, 2017 9:48AM - 10:00AM |
A3.00010: The effects of interfacial polarization on long-range interaction between aqueous phases in oil Meng Shen, Honghao Li, Monica Olvera de la Cruz Metal ions are encapsulated in metalloamphiphile phase together with the counter-ions, and then dispersed in oil in extractive metallurgy. It is found in recent experiments and atomistic simulations that the neutral ion-containing phases are prone to aggregation due to long-range inter-capsule attractions, counterintuitive with the otherwise short-range dipolar interactions. To understand this long-range attraction, we perform coarse-grained simulations that considers interfacial polarization, and track the ion-ion, ion-polarization, and polarization-polarization inter-capsule interactions. The effects of ion size and valency, ion concentration, capsule size and curvature, and permittivity contrast are investigated. Our results show that the inter-capsule ion-ion interaction is significantly increased in the presence of polarization due to redistribution of ions, furthermore, the inter-capsule ion-polarization interaction is comparable with inter-capsule ion-ion interactions. The redistribution of ions potentially leads to local deformation of the capsules. The research paves the way for understanding self-assembly in phases mixed in oil that are ubiquitous in biological systems. [Preview Abstract] |
Monday, March 13, 2017 10:00AM - 10:12AM |
A3.00011: No-slip and anomalous behavior at the liquid/solid interface Justin Pye, Clay Wood, Justin Burton The vast majority of problems in fluid mechanics assume a no-slip condition at the liquid/solid interface. In the last few decades, a number of controlled experiments have found that the no-slip assumption is violated, however, there is little agreement as to the origin and magnitude of the slip. We report new stringent limits on intrinsic slip at a liquid/solid interface. By growing a drop of one liquid (water) on a quartz crystal microbalance (QCM) surface while the system is immersed in a second, matched liquid (undecane), we obtain a high-precision, differential measurement which minimizes systematic effects due to stress, temperature, etc. Our results on all surfaces investigated thus far, including plasma cleaned gold and glass as well as two different self-assembled monolayers (SAMs), show relative slip lengths of 2 nm or less, regardless of contact angle, suggesting that any slip effects are confined to the first few molecular layers in the liquid. In addition to molecular-scale slip lengths, we see anomalous dissipation on the SAM surfaces that cannot be explained by simple slip models. We will also discuss the effects of fluorinated SAM surfaces and a variety of other liquids in the experiments. [Preview Abstract] |
Monday, March 13, 2017 10:12AM - 10:24AM |
A3.00012: Origin of Viscosity in Water by Inelastic X-ray Scattering Takeshi Egami, Takuya Iwashita, Bin Wu, Wei-Ren Chen, Alfred Baron Atomic collision and caging are the principal origin of viscosity in the hard-sphere model, whereas the role of the attractive force is unclear. We proposed earlier through simulation that excitations to change the local topology of atomic connectivity are the origin of viscosity, and at temperatures above the cooperative crossover temperature, T$_{A}$, the time-scale of bond cutting, $\tau_{LC}$, is equal to the Maxwell relaxation time, $\tau_{M}$ (PRL 110, 205504). To prove this idea by experiment we carried out an inelastic x-ray scattering experiment on water at room temperature. The dynamic structure factor S(Q, E) was determined over a wide range of Q (momentum exchange) up to 9.5 {\AA}$^{-1}$ and E (energy exchange) up to 100 meV, and was double-Fourier-transformed into the van Hove function (vHf) g(r, t). Because hydrogen is almost invisible to x-rays the vHf is dominated by the O-O, thus molecular, correlation. The vHf clearly showed the switching action between the first and second O-O neighbors, and that the time-scale to cut the hydrogen bond, $\tau_{LC}$, is about 0.4 ps. This time-scale is close to $\tau_{M}$ (\textasciitilde 0.34 ps), strongly supporting the equality $\tau_{M} \quad = \quad \tau_{LC}$ as suggested by simulation. [Preview Abstract] |
Monday, March 13, 2017 10:24AM - 10:36AM |
A3.00013: Probing the hydrophobic interaction using high-resolution frequency-modulation AFM Itai Schlesinger, Uri Sivan The hydrophobic interaction has been studied extensively over the past few decades with only partial success. Several mechanisms have been proposed to explain this ubiquitous force but none was fully established. Experimentally, the force has been studied in great detail at distances larger than 2-3 nm where the static AFM and the surface force apparatus that served those measurements were stable. Little is known about the short-range interaction and even its sign. Using a high resolution FM-AFM, which was free of that instability, we succeeded in measuring the full distance dependence of the force and found that the hydrophobic attraction seen at long distances turns into pronounced repulsion at shorter distances (that may nevertheless reach $\sim$3 nm) coupled to an oscillatory force profile. Simultaneous measurements of the dissipative component of the interaction reveal an anomalously large dissipation commencing abruptly at the point where attraction begins. The dissipation is more than two orders of magnitude larger than expected from water viscosity or from similar measurements between hydrophilic surfaces. These findings were traced to the accumulation of air near the hydrophobic surfaces. [Preview Abstract] |
Monday, March 13, 2017 10:36AM - 10:48AM |
A3.00014: Wetting in flatland: Complex interfacial transitions at inhomogeneous solid-gas interfaces Peter Yatsyshin, Miguel A. Duran-Olivencia, Andrew O. Parry, Carlos Rascon, Serafim Kalliadasis Interfaces between the different phases of matter surround us, and since the days of van der Waals have been known to provide key insights into the workings of the atomic world. A classical example of this is the adsorption of liquid films at a planar, homogeneous solid-gas interface. It is well-known that substrates with first-order wetting transitions also exhibit a line of first-order prewetting transitions corresponding to the jump from a thin to a thick adsorbed liquid film. We use classical density functional theory to model adsorption on patterned walls and unravel the zoo of associated interfacial phase transitions and its complexity. We show that the thick prewetting film can nucleate at a lower pressure and to continuously spread out across the surface as the prewetting line is approached, thus manifesting ``complete prewetting’’ in flatland. We also interrogate a planar wall chemically patterned with a deep stripe of a different material. This introduces interfacial unbending from the stripe into the picture. Surprisingly, for thin stripes, the lines of prewetting and unbending may merge, leading to a new two-dimensional wetting transition occurring along the walls. Our results may have ramifications for the design of lab-on-a-chip devices and controlled nanofluidics. [Preview Abstract] |
Monday, March 13, 2017 10:48AM - 11:00AM |
A3.00015: Cooperative Activated Transport of Dilute Penetrants in Viscous Molecular and Polymer Liquids Kenneth Schweizer, Rui Zhang We generalize the force-level Elastically Collective Nonlinear Langevin Equation theory of activated relaxation in one-component supercooled liquids to treat the hopping transport of a dilute penetrant in a dense hard sphere fluid. The new idea is to explicitly account for the coupling between penetrant displacement and a local matrix cage re-arrangement which facilitates its hopping. A temporal casuality condition is employed to self-consistently determine a dimensionless degree of matrix distortion relative to the penetrant jump distance using the dynamic free energy concept. Penetrant diffusion becomes increasingly coupled to the correlated matrix displacements for larger penetrant to matrix particle size ratio (R) and/or attraction strength (physical bonds), but depends weakly on matrix packing fraction. In the absence of attractions, a nearly exponential dependence of penetrant diffusivity on R is predicted in the intermediate range of 0.2\textless R\textless 0.8, and the various high packing fraction results collapse well onto a master curve if R is scaled by the matrix transient localization length. Calculations are performed for real thermal liquids based on an a priori mapping to a reference hard sphere mixture. [Preview Abstract] |
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