Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session D04: Water Dynamics in Different Environments: Experiment and Theory II. IceFocus
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Sponsoring Units: DCP DCOMP DBIO DSOFT Chair: Teresa Head-Gordon, University of California, Berkeley Room: 109 |
Monday, March 2, 2020 2:30PM - 3:06PM |
D04.00001: Interfacial water: from atmospheric ice nucleation to nano-confinement Invited Speaker: Angelos Michaelides Recent work from our research group in which we are trying to understand the intimate molecular level details of water freezing will be discussed. A particular emphasis will be placed on the role the surfaces of foreign materials play in accelerating the nucleation process [1-3] and on the dynamical nature of the nucleation event. |
Monday, March 2, 2020 3:06PM - 3:18PM |
D04.00002: Atomic imaging of edge structure and growth of a two-dimensional hexagonal ice Runze Ma, Duanyun Cao, Chongqin Zhu, Ye Tian, Jinbo Peng, Jing Guo, Ji Chen, Xin-Zheng Li, Joseph S Francisco, Xiao Cheng Zeng, Limei Xu, Enge Wang, Ying Jiang The formation and growth of water ice layers on surfaces and of low-dimensional ice under confinement are common occurrences. While structured water adlayers and 2D ice have been imaged, capturing metastable or intermediate edge structures involved in their growth is extremely challenging due to their fragile and short-lived nature. |
Monday, March 2, 2020 3:18PM - 3:30PM |
D04.00003: Simulating Energy Relaxation in Pump–Probe Vibrational Spectroscopy of Hydrogen-Bonded Liquids Riccardo Dettori, Michele Ceriotti, Johannes Hunger, Luciano Colombo, Davide Donadio We introduce a nonequilibrium molecular dynamics simulation approach, based on the generalized Langevin equation, to study vibrational energy relaxation in pump-probe spectroscopy. A colored noise thermostat is used to selectively excite a set of vibrational modes, leaving the other modes nearly unperturbed, to mimic the effect of a monochromatic laser pump. Infrared pump-probe spectroscopy provides detailed information about the dynamics of hydrogen-bonded liquids. Due to the dissipation of the absorbed pump pulse energy, thermal equilibration dynamics also contribute to the observed signal. Disentangling this contribution from the molecular response remains a challenge. By performing non-equilibrium molecular dynamics simulations of hydrogen-bonded liquids, we show that faster molecular vibrational relaxation and slower heat diffusion are decoupled and occur on different length scales. Transient structures of the hydrogen bonding network influence thermal relaxation by affecting thermal diffusivity over a length scale of several nanometers. Energy relaxation is probed by analyzing the evolution of the system after excitation in the microcanonical ensemble, thus providing direct information about the energy redistribution paths at the molecular level and their time scale. |
Monday, March 2, 2020 3:30PM - 3:42PM |
D04.00004: Complete Lattice Vibration Dispersion Curves (36 Branches) for the Frozen (T=0K) Bernal-Fowler Hexagonal Close Packed Crystalline Ice with Four Water Molecules in One Primitive Unit Cell Containing 8 Protons and 4 Oxygen Nuclei Bin Jie, Cindy Tianhui Jie, Chih-Tang Sah In 1969, Faure computed the lowest 12 branches of dispersion curves of lattice vibrational modes for Ice Ih, assuming the water molecule H2O in the crystalline ice as point mass (PM), in order to analyze the experimental infrared and Raman spectra of ice. In 1973, Bosi-Tubino-Zerbi removed the PM approximation of H2O in the 1933 Bernal-Fowler Hexagonal Close Packed (HCP) Primitive Unit Cell (PUC) containing 4 H2O (8 protons and 4 Oxygen nuclei) in order to account for the experimental spectra in the low vibrational frequency (LVF) range. During 1969-2019 (50 years) theoretical and experimental spectra of hexagonal Ice Ih are lacking in the high vibrational frequency (HVF) range. Our 2013 melted-ice model for pure liquid water, demonstrated the dominance of the HVF modes in accounting for the abnormally high mobilities of positive and negative ions in pure liquid water. This talk gives the computed 36 branches of dispersion curves of Ice Ih at 0K, using six prime force constants, four values of which from isolated water molecule, further proving the connection of water’s crystalline solid phase and single molecule gas phase, by our 2013 melted-ice lattice model for the liquid phase of water. |
Monday, March 2, 2020 3:42PM - 4:18PM |
D04.00005: Probing interfacial water by H-sensitive and non-invasive scanning probe microscopy Invited Speaker: Ying Jiang Water/solid interfaces are a central theme across an incredibly broad range of scientific and technological processes. Scanning probe microscopy (SPM) has been extensively applied to probe interfacial water in many interdisciplinary fields. However, there exist two longstanding limitations in the past two decades, which makes SPM fall short compared with conventional spectroscopic methods. First, H atoms of water molecule are very small and light, so it is very difficult to image them directly; Second, the water molecules are linked by weak H bonds, and it is highly possible to disturb the fragile water structure during the imaging process. In order to overcome these two grand challenges, we have developed a new-generation SPM based on a qPlus sensor, which is sensitive to H and non-invasive to water structure [1]. The key lies in probing the high-order electrostatic force between the quadrupole-like CO-terminated tip and the polar water molecules at large tip-water distances. In this talk, I will first discuss the application of this technique to determine the microscopic structure of metastable water clusters [1]. In addition, we have unraveled the detailed atomic structures of ion hydrates at interfaces and discover a magic-number effect on the transport of ion hydrates [2]. Finally, I will show the ability of visualizing the growth of a two-dimensional ice in real space with atomic resolution, by capturing various metastable and intermediate structures during the ice growth at the ice edges [3]. |
Monday, March 2, 2020 4:18PM - 4:30PM |
D04.00006: Computed Lattice Vibration Frequency Spectra Explain the Abnormally High Electrical Mobilities of Positive and Negative Ions in Pure Liquid Water Using the Vibrational Force Constants of Oxygen and Hydrogen (Proton) Nuclei in its Solid and Gas Phases. Chih-Tang Sah, Cindy Tianhui Jie, Bin Jie Our 2013 melted ice model extends the 1933 Bernal-Fowler Hexagonal Close Packed Ice crystal model to pure liquid water (0-100C). The periodically-extended 2 trisector proton sites between 2 nearest neighbor oxygen nuclei, occupied or unoccupied by a proton, are the 2 physical spaces for the migrations of the 2 protonic fermion species, the protons and prohols. The physical space describes, in the statistically large sensible volume, the 2 protonic energy bands, for protons migrating among the unoccupied proton sites and prohols migrating among the occupied proton sites. The vibrational modes of the protons and oxygens give the 2 atomic phonon species: 12 oxygenic bosons in the low energy range and 24 protonic bosons in the high energy range. Electrical charge and inertia mass transports in pure liquid water, are carried by the protons, and dominated by the strong localized (local mode & self trap) interaction between the protonic fermions and protonic bosons, with noisy background from the oxygenic bosons. Our computed temperature variations (0–100C) of the three parameters (the proton product and the two protonic mobilities) are in excellent agreement with the international handbook values. |
Monday, March 2, 2020 4:30PM - 4:42PM |
D04.00007: Nanoindentation of Ice Ih - Atomistic simulations Pedro Antonio Santos-Flórez, Carlos Javier Ruestes, Maurice De Koning Using molecular dynamics simulations we study the mechanical response of ice Ih through nanoindentation tests perpendicular to the basal plane. Using a smooth spherical tip represented by a repulsive potential we explore the deformation mechanisms and hardness estimates for ice as described by the all-atom TIP4P/Ice potential and the coarse-grained mW models. We assess the sensitivity to the tip radius and the penetration rate both for low temperatures as well as for conditions close to the melting point, where the formation of a quasi-liquid layer (QLL) on the surface becomes relevant. We find that during plastic deformation the main mechanism for stress relief for the low temperatures is the amorphization of the crystalline ice bilayers. On the other hand, for high temperatures the plastic deformation occurs by bilayer-by-bilayer melting, consistent with previous literature. Considering the difference between the behaviors of the mW and TIP4P/Ice models, we observe that the latter also involves the nucleation and motion of dislocations. This is consistent with recent observations concerning uniaxial deformations and provides further indications that the absence of explicit protons in the mW model gives rise to excessive ductility. |
Monday, March 2, 2020 4:42PM - 4:54PM |
D04.00008: Sum Frequency Generation Spectroscopy of Ice/Air and Water/Air Interfaces from Ab Initio Deep Potential Molecular Dynamics Marcos Andrade, Linfeng Zhang, Annabella Selloni, Roberto Car The interfaces of liquid water and ice with air abound on Earth and impact non-negligibly atmospheric sciences. Directly probing the structure of interfacial water is challenging, and the surface-specificity of Sum Frequency Generation (SFG) spectroscopy has offered important insights on both structure and dynamics of interfacial water and ice. Ab initio molecular dynamics (AIMD) could, in principle, aid interpret the experimental observations since it accesses both molecular and electronic structure of interfacial water. However, AIMD stumbles on the slow convergence of the SFG spectrum with simulation time. We here overcome this difficulty using Deep Neural Networks (DNN) to represent the ab initio potential energy surface. DNNs were also used to obtain molecular dipole moment and polarizability of water in agreement with first-principles methods, which allows a proper computation of the SFG spectrum of water/air and ice/air interfaces relying only on the dipole approximation. Our method can be easily extended to other interfaces and should enable ab initio level simulations of SFG spectra for a wide variety of systems. |
Monday, March 2, 2020 4:54PM - 5:06PM |
D04.00009: How crystals form: a theory of nucleation pathways. James Lutsko Classical Density Functional theory is combined with fluctuating hydrodynamics to describe nucleation in general and crystallization in particular. The nucleation pathway is characterized as the most likely path connecting the initial homogeneous solution to the critical cluster[1]. Classical Nucleation Theory can be recovered with additional approximations[2]. Results for a Lennard-Jones system[3] show a two-step path with the formation of a dense fluid-like droplet followed by the development of order within. During ordering, the system passes through a metastable, subcritical phase that could be identified as a nucleation precursor. The precuror is a sub-critical crystalline cluster stabilized by completed crystalline shells and a wetting layer. |
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D04.00010: Surface and bulk contributions to sum-frequency vibrational spectroscopy of single crystalline ice Xu Xiaofan, Yuen-Ron Shen, Chuanshan Tian We study the bulk and surface contributions to the sum-frequency vibrational spectroscopy (SFVS) of ice Ih(0001) interfaces in the bonded OH stretching band at 223K. Using phase-sensitive SFVS with selected polarization combination and beam geometry, a pure electric quadrupole SF spectrum from bulk ice was obtained. Base on analysis of selection rule, an electric quadruple sub-band near 3120 cm-1 originated from the bulk was found to constitute large portion in the reflected SF spectrum of vapor/ice interface. Via modification of ice surface by absorption of a monolayer of ethanol, the SF vibrational spectrum was significantly reduced at ~3170 cm-1, suggesting the surface is also important in the ice SF spectrum. These results not only reveal the importance of bulk contribution in SFVS spectrum of ice, but pave the way for investigation of ice surface, e.g. surface premelting, in practical environments. |
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