Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session A03: Disorder and Fluctuations in Chemical Physics IFocus
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Sponsoring Units: DCP Chair: Sapna Sarupria, University of Minnesota Room: Room 126 |
Monday, March 6, 2023 8:00AM - 8:36AM |
A03.00001: A non-equilibrium thermodynamic route for control: From activity patterns in cytoskeletal networks to memory Invited Speaker: Suriyanarayanan Vaikuntanathan Biological materials, such as the actin cytoskeleton, exhibit remarkable structural adaptability to various external stimuli by consuming different amounts of energy. Using methods from large deviation theory we identify a thermodynamic control principle for structural transitions in a model non-equilibrium cytoskeletal network. Our work demonstrates how a thermodynamic quantity can be used to renormalize effective interactions, which in turn can tune structure in a predictable manner, suggesting a thermodynamic principle for the control of cytoskeletal structure and dynamics. In the second part of the talk, we will explore how non- equilibrium activity can be used to endow materials with memory storage and recall properties, in some cases far in excess of what is allowed at equilibrium. Together, these results identify potential ways in which non-equilibrium forcing may be used to create adaptive information processing materials. |
Monday, March 6, 2023 8:36AM - 8:48AM |
A03.00002: Steady-like topology of the hydrogen bond network in supercooled water Fausto Martelli We investigate the link between topology of the hydrogen bond network (HBN) and large-scale density fluctuations in water from ambient conditions to the glassy state. We observe a transition from a temperature-dependent topology at high temperatures, to a steady-like topology below the Widom temperature TW ∼ 220 K signaling the fragile-to-strong crossover and the maximum in structural fluctuations. As a consequence of the steady topology, the network suppresses large-scale density fluctuations much more efficiently than at higher temperatures. Below TW, the contribution of coordination defects of the kind A2D1 (two acceptors and one donor) to the kinetics of the HBN becomes progressively more pronounced, suggesting that A2D1 configurations may represent the main source of dynamical heterogeneities. Below the vitrification temperature, the freezing of rotational and translational degrees of freedom allow for an enhanced suppression of large-scale density fluctuations and the sample reaches the edges of nearly hyperuniformity. The formed network still hosts coordination defects, hence implying that nearly hyperuniformity goes beyond the classical continuous random network paradigm of tetrahedral networks and can emerge in scenarios much more complex than previously assumed. Our results unveil a hitherto undisclosed link between network topology and properties of water essential for better understanding water’s rich and complex nature. Beyond implications for water, our findings pave the way to a better understanding of the physics of supercooled liquids and disordered hyperuniform networks at large. |
Monday, March 6, 2023 8:48AM - 9:00AM |
A03.00003: Revealing the Flexibility of Hydrogen Bond Networks in Hexagonal Ice by Frozen Liquid-Cell Electron Microscopy Jingshan S Du, James J De Yoreo Ice crystals are formed by directional hydrogen bonds between water molecules and are thus considerably more flexible than typical inorganic structures based on covalent or ionic bonds. However, it is challenging to visualize such a crystalline network with atomic resolution in real space due to the weak bond strength and the resulting instability of ice under electron irradiation in vacuo. In this presentation, we report high-resolution transmission electron microscopy (HRTEM) of ice sections encapsulated between amorphous carbon membranes. Specifically, liquid cells containing water were frozen by liquid nitrogen to form hexagonal ice (Ih ice). Even though the ice section shows overall single-crystallinity by diffraction standards, the crystal exhibits structural variation and contains sub-domains sized on the 10-nm scale. Quantitative strain and tilt mapping reveals the sub-surface flexibility of ice and is used to demonstrate the correlation between defect structures and strain accumulation. We discovered that both sharp low-angle grain boundaries and gradual bending of the crystal are accountable for forming sub-domains with different crystal orientations. Taken together, this work shows promise in elucidating the molecular and defect structures in ice and may shed light on the physics of ice surfaces and sub-surfaces. |
Monday, March 6, 2023 9:00AM - 9:12AM |
A03.00004: Manifestations of the structural origin of water's anomalies in the heterogeneous relaxation on the potential energy landscape Rakesh S Singh Liquid water is well-known for its intriguing thermodynamic anomalies in both the normal and the supercooled states. The phenomenological two-state models based on the assumption of the existence of two types of competing local states in liquid water have been extremely successful in describing the thermodynamic anomalies of water. However, the precise structural and energetic features of these two types of competing local states in liquid water still remain elusive. In this study, we have employed a predefined structural order parameter-free approach to unambiguously identify the two types of interconvertible local states with significantly different structural and energetic features in the TIP4P/2005 liquid water. This identification is based on the heterogeneous relaxation of the thermally equilibrated structures in the potential energy landscape (PEL) during the steepest-descent energy minimization. We have further established a direct relationship between the population fluctuation of the two types of local states and the anomalous thermodynamic behavior of supercooled water. Additionally, this study unravels the signatures of the supercooled water's anomalies encoded in the topography of the PEL of the system. We believe that the generality of the approach proposed here would enable it to be applicable to a broad range of liquids, not necessarily molecular, to provide the precise molecular origin of bulk liquid properties. |
Monday, March 6, 2023 9:12AM - 9:48AM |
A03.00005: Disorder and order in condensed water Invited Speaker: Thomas Loerting H2O as the most anomalous substance and as the key ingredient in all forms of life keeps fascinating the science community. Yet, many open questions remain in our understanding of water. The last 25 years maybe called the era of ice polymorphs, in which the crystal structures of 8 polymorphs, ice XII-ice XIX, were unraveled. All of these polymorphs feature an ordered network of oxygen atoms, but only some of them feature an ordered network of hydrogen atoms. The last 40 years may even be called the era of polyamorphism, in which three distinct amorphous ices were discovered. These can be interconverted in sharp, first-order like transitions and can be cycled back and forth just like thermodynamically stable phases in the phase diagram. Even more thrilling, amorphous ices experience reversible glass-to-liquid transitions in the range between 110 and 160 K. This makes two distinct, deeply supercooled liquids of composition H2O accessible. This recognition represents new physics per se, and it has paved the way to the discovery of novel concepts, for instance the nucleation of low-density liquid H2O in a matrix of high-density liquid H2O, with sharp phase boundaries between the two liquids. This fuels two-liquid theories of water and suggest that our understanding of the anomalies in water requires an understanding of mixing thermodynamics and dynamics. With the knowledge accumulated over the last few decades it is actually now possibe to govern the subnetworks of H and O atoms in H2O independently from each other: it is possible to control oxygen disorder, but also to govern hydrogen order and disorder in an ordered network of oxygen atoms. In my talk I will review some of this new physics and outline where I think the field may head - with the discovery of many more ice phases and with a thorough characterization of the metastable liquid-liquid phase equilibrium in a one-component system ahead of us. |
Monday, March 6, 2023 9:48AM - 10:00AM |
A03.00006: The role of high-density and low-density amorphous ice on biomolecules at cryogenic temperatures: a case study with polyalanine Ali H Eltareb, Nicolas Giovambattista, Gustavo Lopez Experimental techniques, such as cryo-electron microscopy, require biological samples to be recovered at cryogenic temperatures (T ≈ 100 K) with water being in an amorphous ice state. However, (bulk) water can exist in two amorphous ices at P |
Monday, March 6, 2023 10:00AM - 10:12AM |
A03.00007: Neutron Scattering Investigation of the Liquid-Liquid Transition in Confined Water Souleymane Diallo, Douglas L Abernathy, Jiao Lin We present deep inelastic neutron scattering investigation (DINS) of water confined in the nanopores of hydrophilic silica compounds with two different average pore sizes, respectively 16 Å and 39 Å. The goals of these measurements are (1) to identify potential changes in the proton momentum distribution n(p) as the temperature is reduced through the putative “fragile” liquid to “strong” liquid crossover temperature TL, and (2) to determine the lineshape of the corresponding n(p) for comparison with results in other confining media and in bulk water. |
Monday, March 6, 2023 10:12AM - 10:24AM |
A03.00008: Generalized Framework for Modeling Water Confined Inside Metallic and Semiconducting Carbon Nanotubes Rahul Prasanna Misra, Daniel Blankschtein Carbon nanotubes (CNTs) with diameters in the 0.8 nm – 2 nm range are emerging as important material platforms to investigate confinement-induced effects on water and electrolyte solutions, which has wide-ranging applications in electrochemistry, energy, and membrane science. Although previous molecular dynamics simulation studies have attempted to elucidate the nature of water-CNT dispersion interactions modeled using pair-wise additive potentials, including the Lennard-Jones potential, it remains unclear how the anisotropic polarizability tensors of CNTs, i.e., the different polarizability components along the radial and axial directions, govern the properties of polar fluids such as water, under nanoscale confinement. Importantly, while both metallic and semiconducting CNTs have a radial polarizability which scales quadratically with the CNT radius, these CNTs differ significantly in their axial polarizability which depends on the band gap. Here, we present a generalized theoretical framework for modeling water confined inside metallic and semiconducting CNTs, and investigate the thermodynamic (e.g., density, hydrogen-bonding network) and transport (e.g., friction coefficient) properties of confined water molecules as a function of the CNT radial and axial polarizability. Specifically, we show how the water-induced electronic polarization of the CNT results in the generation of an electrostatic pressure which then acts back on the confined water molecules, including influencing the water density and structuring. Overall, our study highlights the central role of electronic polarization effects in nanofluidics involving polar fluids confined inside strongly polarizable nanomaterials. |
Monday, March 6, 2023 10:24AM - 10:36AM Author not Attending |
A03.00009: Mapping out the Hydration Layer "Fingerprint" with Overhauser Dynamic Nuclear Polarization John M Franck A common mental model for biological macromolecules represents proteins as secondary structural elements with side-chains whose interactions are motivated by a combination of charge, hydrophobicity, and spatial fit (i.e. sterics and so-called "lock and key" mechanisms). This powerful model has yielded many important modern-day results. However, macromolecules are dramatically multi-dimensional systems and therefore exhibit interactions and motions governed not by intuitive potentials operating under spatial constraints, but by free energy. This is nowhere more apparent than when considering the layers of water and/or lipids that coat protein surfaces. Different patches of this "hydration layer" can display dramatically different enthalpies and entropies -- resulting in measurably different translational and rotational mobilities. |
Monday, March 6, 2023 10:36AM - 10:48AM |
A03.00010: Computational Evidence for the Crucial Role of Dipole Cross-Correlations in Polar Glass-Forming Liquids Kajetan Koperwas It is commonly believed that the dipole-diploe cross-correlations do not contribute to the total dipole correlation function, which is directly probed in the Dielectric Spectroscopy experiment. However, our study of the dipole-dipole correlations obtained from the molecular dynamics simulations for strongly and weakly polar model liquids sheds new light on the above conviction. The obtained results indicate that the cross-correlations' contribution to the system's total dipole moment correlation function is negligible only for weakly polar liquids. In contrast, the cross-correlations term dominates over the self-correlations term for the examined strongly polar liquid. Consequently, our studies strongly give fundaments for the suggested in the literature correlation between the shape of the dielectric spectra and the value of the dipole moments (Phys. Rev. Lett 116, 025702, 2016) well as they support the interpretation of the dielectric spectra nature of glass-forming liquids recently proposed by Pabst et al. (J.Phys. Chem. Lett. 12, 3685, 2021) |
Monday, March 6, 2023 10:48AM - 11:00AM |
A03.00011: A novel approach to characterize the relationship between dissociation and conductivity in ionic liquid and solvent mixtures Pierre Walker, Zhen-Gang Wang Ionic liquid and solvent mixtures, in the recent development of electrochemical energy storage devices, such as supercapacitors and batteries, have emerged as promising potential avenues due to their high ionic conductivity. Particularly, the fraction of dissociated ions is thought to be highly influential on ionic conductivity, yet the nature of the link between the two properties has not been well established. In this work, we develop a novel theoretical approach, based on Wertheim’s thermodynamic perturbation theory and Turq et al.’s mean-spherical-approximation theory to rigorously connect ion dissociation and conductivity. We have validated this approach with molecular dynamics simulations for a large range of ionic liquid chemistries and solvent mixtures. A key insight is that although one might expect the dielectric medium to be the determining factor in ion dissociation, we find that the solvent dipole moment drives dissociation. Furthermore, we show that the Nernst–Einstein conductivity is directly proportional to ion dissociation. This novel approach could be used to predict the ionic conductivity of ionic liquid and solvent mixtures, aiding in the computer-aided molecular design for specific applications, such as battery electrolytes. |
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