Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session E57: Physics of Liquids IIIFocus
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Sponsoring Units: GSNP Chair: Yang Zhang, University of Illinois at Urbana-Champaign Room: BCEC 256 |
Tuesday, March 5, 2019 8:00AM - 8:36AM |
E57.00001: Can Statistical Physics Concepts Shed Some Light on the 73 Anomalies of Liquid Water? Invited Speaker: H Stanley We focus on recent progress in understanding the 73 anomalies of water, by combining information provided by recent experiments and simulations on water in bulk, nanoconfined and biological environments designed to test the hypothesis that liquid water has behavior consistent with the novel phenomenon of “liquid polymorphism” in that low-temperature water can exist in two distinct phases [1,2]. We will utilize the properties of the Widom line—the locus of maximum correlation length—which can be measured experimentally at temperatures well above the critical temperature. Finally, we will discuss how the general concept of liquid polymorphism is proving useful in understanding anomalies in other liquids, such as silicon, silica, and carbon which have in common that they are characterized by two characteristic length scales in their interactions. |
Tuesday, March 5, 2019 8:36AM - 8:48AM |
E57.00002: Liquid-Liquid Phase Transition in Metallic Alloy Melts Detected by Nuclear Magnetic Resonance En-Yi Chen, Wei-Ming Yang, Alfred Kleinhammes, Yue Wu Liquid-liquid phase transition (LLPT) is thought to be exotic as it is not obvious what order parameters could be associated with qualitative changes in liquid structures. In some special cases where the valency of the element and bonding characters change substantially with pressure and temperature, such as the case of phosphorus and cerium, LLPT could take place accompanied by clear changes of the density. Here we show that non-density-driven LLPT can actually be common in metallic alloys, taking place above the liquidus temperature Tliq. High-temperature NMR is shown to be an effective tool for revealing such LLPT facilitated by its high sensitivity and high resolution. Subtle changes are detected that are difficult to detect by conventional thermodynamic measurement techniques. We will discuss the observation of LLPT in La-based alloys and Al-based alloys. We will show that the corresponding density change is exceedingly small. In addition, the kinetics of the transition process is also characterized systematically by NMR. This shows that the LLPT should have a profound influence on alloy solidifications. |
Tuesday, March 5, 2019 8:48AM - 9:00AM |
E57.00003: Liquid lipid phase separation on curved surfaces Melissa Rinaldin, Piermarco Fonda, Luca Giomi, Daniela Jutta Kraft By using colloid supported lipid bilayers of designed shape we proved how the interplay of the shape and the composition of a closed membrane determines the likelihood, the position and the composition of liquid domains [1]. Here, we show that if we open the membrane by connecting it to a reservoir of lipids, all these three properties are deeply affected. In particular, the pinning of the softer domains in high curvature regions is enhanced, leading to a consistent pattern on all colloids. |
Tuesday, March 5, 2019 9:00AM - 9:12AM |
E57.00004: Genetic Competition in Weakly Compressible Turbulent Flows Roberto Benzi, Giorgia Guccione, Abigail Plummer, David Robert Nelson, Federico Toschi The genetic competition for biological species living in marine environments can be severely influenced by fluid advection. Very often, in oceans and in lakes, cell generation times are precisely in the inertial range of eddy turnover times and therefore the influence of turbulence must be properly taken into account. We employ both an off-lattice agent-based simulation as well as an on-site density-based model to describe two competing populations in one and in two spatial dimensions under the influence of advecting (turbulent) velocity fields. The novel on-site density-based model allows us to accurately and efficiently describe the dynamics of the population and the genetics of a large number of individuals, making this the ideal tool to study populations in two dimensions. We find that the presence of compressible turbulent velocity fields can have a strong effect on genetic competitions. Even in regimes where the overall population structure is approximately unaltered, the flow can significantly diminish the effect of a selective advantage on fixation probabilities. We explain this effect in terms of the enhanced survival of organisms born at the sources in the flow and the influence of Fisher genetic waves. |
Tuesday, March 5, 2019 9:12AM - 9:24AM |
E57.00005: Structure and Dynamics of Water Interacting with Hydrophilic, Nanostructured CuO Coatings1 James Torres, Zachary Buck, Helmut Kaiser, Xiaoqing He, Tommi White, Robert Winholtz, Haskell Taub, Madhusudan Tyagi, Kenneth W Herwig, Eugene Mamontov, Luke L Daemen, Michelle Kidder, Flemming Y Hansen We have used neutron scattering and electron microscopy to investigate how the structure, dynamics, and phase transitions of water near a bare copper surface are affected by coating it with strongly hydrophilic CuO nanostructures. Our high-energy-resolution elastic neutron scattering measurements show the abrupt freezing transition of water near a bare Cu surface is spread into a continuous transition spanning a temperature range of ~80 K upon coating with the CuO nanostructures. From these elastic scans, we infer the presence of at least two distinct water populations, differing in their freezing behavior and their proximity to the nanostructures. Quasielastic neutron scattering measurements support this interpretation by providing evidence of three water components diffusing on different time scales. Our environmental-SEM images reveal micron-size water droplets wet to the nanostructures. In addition, neutron diffraction measurements indicate that the water closest to the CuO nanostructures freezes into an amorphous solid, while more distant water freezes into crystalline ice. The presence of the two forms of ice is consistent with vibrational spectra observed by inelastic neutron scattering. |
Tuesday, March 5, 2019 9:24AM - 9:36AM |
E57.00006: The molecular description of amorphous ices and the mechanism governing their pressure induced interconversion Fausto Martelli, Roberto Car, Nicolas Giovambattista We employ classical molecular dynamics simulations to investigate the molecular-level structure of water during the isothermal compression of hexagonal ice (Ih) and low-density amorphous (LDA) ice at low temperatures to high-density amorphous ice (HDA) [1], and the isothermal decompression of HDA by employing a sensitive local order metric [2]. Our results confirm that LDA and HDA are indeed amorphous, i.e., they lack of polydispersed ice domains. Interestingly, HDA contains a small number of domains that are reminiscent of the unit cell of ice IV, although the hydrogen-bond network (HBN) of these domains differ from the HBN of ice IV. Both nonequilibrium LDA-to-HDA and Ih-to-HDA transformations are two-steps processes where a small distortion of the HBN first occurs at low pressures and then, a sudden, extensive re-arrangement of hydrogen bonds at the corresponding transformation pressure follows. |
Tuesday, March 5, 2019 9:36AM - 9:48AM |
E57.00007: Multiple Protonic Kinetic Energy Band Models of Melted Ice Periodic Lattice for Pure Liquid Water Bin Jie, Tianhui Jie, Chih-Tang Sah Existence of long-range order in fluid water under numerous daily conditions led us to extend the 1933 Bernal-Fowler Hexagonally Close Packed (HCP) crystalline ice lattice to model pure liquid water as Melted Ice. The 8 protons in the primitive unit cells (PUC) of the HCP lattice vibrate about their lattice positions, jump among the 16 possible proton sites, half empty and half occupied in the PUC and transport among the PUC's. Propagating and localized proton vibrations are respectively the Protonic Fermions and Bosons, described by the Bloch and Wannier eigenfunctions, which are perturbed to form localized states (protonic traps) by rare random localizations. The eigenvalues of the frozen periodic lattice give the kinetic energy-band landscapes of the protonic Fermions and Bosons, while the long-range order in fluid water led us to model the proton transport by our 3-step (A, B, C) collision dynamics (DDGRT). The observed 3 thermal activation energies of pH and positive and negative ion electrical mobilities, are in excellent agreement with Slinky Toy Model of the proton vibration frequencies of dilute vapor water, providing the existence proof for this new two-phase approach to model liquid water, employing ice lattice and random distribution of water molecules in vapor. |
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