Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session L3: Focus Session: Solvation, Dynamics, and Reactivity in Complex Environments I |
Hide Abstracts |
Sponsoring Units: DCP Chair: Valeria Molinero, University of Utah Room: 107 |
Wednesday, March 5, 2014 8:00AM - 8:12AM |
L3.00001: Dynamic response in electric field-induced nanowetting in salt solution Dusan Bratko, Davide Vanzo, Alenka Luzar Electric field applied across hydrophobic nanopores can control wetting/dewetting transitions. This switching effect is of potential importance in applications from fluid flow control in nanofluidics to imbibition of nanoporous materials to surface energy absorption and storage. Dynamic response to the imposition or cessation of the field occurs at two stages characnterized by different timescales. Fast response, O(ps), involves the change in the effective surface tension, which takes place along with water polarization. Slower response, associated with wetting/dewetting transitions involves solution infiltration or expulsion, an activated process we show to be kinetically viable only in nanoscale pores. Using molecular dynamics simulations, we identify a window of conditions where O(ns) responses of the wetting/expulsion cycle can be secured for experimentally realizable fields, porosity and salinity of the solution. [Preview Abstract] |
Wednesday, March 5, 2014 8:12AM - 8:24AM |
L3.00002: First-principles investigation of boron incorporation into CRUD under Pressurized Water Reactor conditions Zs. Rak, C.J. O'Brien, D.W. Brenner CRUD (Chalk River Unidentified Deposit) is predominately a nickel-ferrite deposit on hot surfaces of nuclear fuel rods during reactor operation. The presence of CRUD modifies the core-coolant heat transfer and can induce localized corrosion on the cladding surface. Besides these unwanted effects boron, which is a neutron absorber, can accumulate within the CRUD, triggering shifts in the neutron flux and fluctuations in the reactor power level. Therefore, it is crucial to understand and predict the mechanisms by which B is trapped into the CRUD. As a first step, the incorporation of B defect into the crystal structure of NiFe$_{2}$O$_{4}$ has been investigated using the DFT framework. To obtain the formation energies of various interstitial and substitutional B-defects, theoretical results have been combined with experimental thermo-chemical data. Assuming solid-solid equilibrium conditions, the main factors that limit the incorporation of B are (i) the narrow stability domain of the host NiFe$_{2}$O$_{4}$ and (ii) the formation of ternary Fe-B-O and Ni-B-O compounds. The study also investigates the incorporation of B assuming solid-liquid equilibrium between NiFe$_{2}$O$_{4}$ and the surrounding aqueous solution under conditions of pressure, temperature, and pH characteristic to pressurized water reactors. [Preview Abstract] |
Wednesday, March 5, 2014 8:24AM - 8:36AM |
L3.00003: Atomistic Models for High-throughput Prediction of Hydration Free Energies Jianzhong Wu The classical density functional theory (DFT) is proposed as an efficient computational tool for high-throughput prediction of the solvation free energies of small molecules in liquid water at the ambient condition. With the solute molecules represented by the AMBER force field and the TIP3P model for the solvent, the new theoretical method predicts the hydration free energies of 500 neutral molecules with average unsigned errors of 0.96 kcal/mol and 1.04 kcal/mol in comparison with the experimental and simulation data, respectively. The DFT predictions are orders of magnitude faster than conventional molecular dynamics simulations and the theoretical performance can be further improved by taking into account the molecular flexibility of large solutes. [Preview Abstract] |
Wednesday, March 5, 2014 8:36AM - 9:12AM |
L3.00004: Collisions of Sodium Atoms with Liquid Glycerol: Insights into Na Atom Solvation and Ionization and the Reactions of Near-Interfacial Electrons Invited Speaker: Gilbert Nathanson Over the last 70 years, thousands of reactions between solvated electrons and dissolved species have been investigated in water and other protic solvents. Electrons born at the surface of the solvent, however, may react differently than those created within it. We have explored this interfacial reactivity by directing sodium atoms at the surface of liquid glycerol in vacuum. Gas-liquid scattering experiments show that electrons generated from the Na atoms produce hydrogen atoms and hydrogen molecules, hydroxide ions and water, and glycerol fragments. Remarkably, nearly half the hydrogen atoms created near the surface escape into vacuum before reacting with the solvent. Complementary ab initio molecular dynamics simulations of Na striking a 17-molecule glycerol cluster indicate that the glycerol hydroxyl groups reorient around the Na atom as it makes contact with the cluster and begins to ionize on the picosecond timescale. The experiments and simulations together indicate that Na-atom deposition provides a low-energy pathway for generating solvated electrons in the near-interfacial region of protic liquids. [Preview Abstract] |
Wednesday, March 5, 2014 9:12AM - 9:24AM |
L3.00005: Measurement of Ultraslow Rotational Dynamics of Probes in Imidazolium-Based Ionic Liquids Near and Below the Glass Transition Temperature: Studying the Role of Structural Heterogeneity on Dynamic Heterogeneity Kayla Mendoza, Rakhitha Udugama-Arachchilage, Fehmi Bardak, George Tamas, Edward Quitevis The dynamics of imidazolium-based ionic liquids were probed in the supercooled liquid regime by observing the fluorescence recovery after photobleaching of directionally oriented tetracene molecules. Spatial heterogeneity arises in ionic liquids containing a 1-alkyl-3-methylimidazolium cation for alkyl chain lengths equal to and exceeding four carbons; aggregation of the alkyl tails leads to the formation of non-polar domains, which increase in size with increasing alkyl chain length. Near the glass transition, supercooled liquids relax non-exponentially, and this non-exponentiality has been attributed to dynamic heterogeneity. The purpose of this study was to observe the role of structural heterogeneity on dynamic heterogeneity. The rotational dynamics of tetracene in 1-butyl-3-methylimidazolium bistriflate, 1, 3-dibutylimidazolium bistriflate, and 1-heptyl-3-methylimidazlium bistriflate were observed in the vicinity of their glass transition temperatures. From the weak dependence of the degree of non-exponentiality exhibited by the relaxation function on alky chain length and cation symmetry, it was concluded that structural heterogeneity does not play a strong role in determining dynamic heterogeneity. [Preview Abstract] |
Wednesday, March 5, 2014 9:24AM - 9:36AM |
L3.00006: CO2 capture in amine solutions from ab initio molecular dynamics Changru Ma, Fabio Pietrucci, Wanda Andreoni The most mature technology for post-combustion CO$_2$ capture exploits a cyclic process, in which CO$_2$ is selectively and reversibly absorbed in an amine solution, typically monoethanolamine(MEA) at 30\%wt concentration. Empirical efforts are ongoing worldwide to reduce the high energy penalty for amine regeneration and to increase the absorption rate. Computer simulations can help by providing new insights and the missing quantitative information. Using extensive large-scale Car-Parrinello molecular dynamics simulations, aided by accelerated sampling techniques, we have characterized the reactions leading to CO$_2$ capture in MEA 30\%wt solutions via the formation of the carbamate, and the subsequent CO$_2$ release. Deprotonation and CO$_2$ release turn out to be competitive for an intermediate zwitterion (free-energy barrier $\sim$10kcal/mol), with sizable entropic contribution, whereas CO$_2$ release from the carbamate has a much higher barrier ($\sim$50kcal/mol), mainly enthalpic and rather independent of temperature. An unprecedented characterization of structural and vibrational properties of the solution allows us to interpret recent experimental results. More results on other amines, allow us to rationalize their still unexplained better performance relative to MEA. [Preview Abstract] |
Wednesday, March 5, 2014 9:36AM - 9:48AM |
L3.00007: \textit{Ab initio} Molecular Dynamics Study of Carbon Dioxide Adsorption on the Ni Catalyst Surface Ji Il Choi, Yong-Hoon Kim The first-principles molecular dynamics simulations can provide insight into the surface reaction mechanisms by including thermodynamic environments and rigorously determining the transition states between reactants and products, which are not available from the static study of the species already adsorbed on the surface. In view of its importance in various energy applications, we here report on the first-principles molecular dynamics study of the chemical reaction of CO$_{\mathrm{2}}$ molecules on the representative atomicallyflat lowMiller-index Ni(111) surface. We adopted the DFT-D2 scheme to properly describe the van der Waals interactions, and considered various thermodynamic conditions including the temperature, pressure, and number of additional molecular species. To analyze the reaction mechanisms, in addition to the change of the electronic structure of CO$_{\mathrm{2}}$ upon adsorption on the Ni surface the energy barriers between the initial and final stages of CO$_{\mathrm{2}}$ deposition were calculated with and without the interactions with neighboring molecules. [Preview Abstract] |
Wednesday, March 5, 2014 9:48AM - 10:24AM |
L3.00008: Probing Intermolecular Interactions in Polycyclic Aromatic Hydrocarbons with 2D IR Spectroscopy Invited Speaker: Amber Krummel Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment and impact geochemical processes that are critical to sustainable energy resources. For example, asphaltenes exist naturally in geologic formations and their aggregates heavily impact the petroleum economy. Unfortunately, the chemical dynamics that drive asphaltene nanoaggregation processes are still poorly understood. Solvent dynamics and intermolecular interactions such as $\pi $-stacking interactions play integral roles in asphaltene nanoaggregation. Linear and nonlinear vibrational spectroscopy including two-dimensional infrared spectroscopy (2DIR), are well suited to explore these fundamental interactions. Teasing apart the vibrational characteristics in PAHs that model asphaltenic compounds represents an important step towards utilizing 2D IR spectroscopy to understand the intermolecular interactions that are prevalent in asphaltene nanoaggregation. A solar dye, N,N'-Dioctyl-3,4,9,10-perylenedicarboximide, is used in this work to model aphaltenes. Carbonyl and ring vibrations are used to probe the nanoaggregates of the model compounds. However, the characteristics of these normal modes change as a function of the size of the conjugated ring system. Thus, in order to fully understand the nature of these normal modes, we include a systematic study of a series of quinones. Our investigation employs a combination of 2DIR spectroscopy and electronic structure calculations to explore vibrational coupling in quinones and PAHs. We compare the calculated vibrational characteristics to those extracted from 2DIR spectra. [Preview Abstract] |
Wednesday, March 5, 2014 10:24AM - 10:36AM |
L3.00009: Freezing and Melting of Salt Hydrates Next to Solid Surfaces Probed by Infrared-Visible Sum Frequency Generation Spectroscopy Emmanuel Anim-Danso, Yu Zhang, Ali Dhinojwala Understanding the freezing of salt solution near solid surfaces is important in many scientific fields. Here, we have used sum frequency generation (SFG) spectroscopy to study the freezing of NaCl solution next to a sapphire substrate. During cooling we observe two transitions; the first transition corresponds to segregation of concentrated brine next to the sapphire surface as we cool the system down into the phase region where there is a coexistence of ice and brine. At this transition, the intensity of the ice-like peak decreases, suggesting the disruption of hydrogen bonding by sodium ions. The second transition corresponds to the formation of NaCl hydrates with abrupt changes in both SFG intensity and the sharpness of spectral peaks. The similarity in the position of the SFG peaks with those observed using IR and Raman spectroscopy indicates the formation of NaCl.2H$_2$O crystals next to the sapphire substrate. Freezing and melting of other hydrates will be discussed. [Preview Abstract] |
Wednesday, March 5, 2014 10:36AM - 10:48AM |
L3.00010: Effects of Aqueous Solvation on the Photochemistry of Pyruvic Acid Allison Reed-Harris, Barbara Ervens, Richard Shoemaker, Rebecca Rapf, Jay Kroll, Elizabeth Griffith, Anne Monod, Veronica Vaida The role of organic compounds in atmospheric chemistry leading to aerosol formation is under investigation due to the necessity to understand the effects of aerosols on global climate change. It has recently been shown that important pathways in formation of organic aerosols are in aqueous environments where high molecular weight products are formed and can potentially contribute to atmospheric aerosol mass. This presentation describes the photochemistry of pyruvic acid in aqueous solutions representative of atmospheric fogs, clouds and wet aerosols. Solvation of pyruvic acid in water completely changes the photodissociation of this molecule compared to its photolysis in the gas phase. The reaction mechanism of pyruvic acid as a function of its environment and concentration will be presented along with the kinetics obtained in aqueous solution. The resulting first order rate constants will be presented to discuss the effect of water as a solvent in this chemistry. These results are input to atmospheric models to evaluate the atmospheric consequences of solvation of pyruvic acid on its atmospheric reactivity and its role in aerosol formation. [Preview Abstract] |
Wednesday, March 5, 2014 10:48AM - 11:00AM |
L3.00011: Collisions and Reactions of HNO$_{3}$ and N$_{2}$O$_{5}$ with Sea Spray Mimics Michael Shaloski, Timothy Bertram, Gilbert Nathanson Heterogeneous reactions occurring at the surface of sea spray aerosol (SSA) droplets can lead to changes in the chemical compositions of the droplet, the denitrification of the atmosphere, and the production of chlorine-containing gases. These processes ultimately influence both ozone and methane concentrations and air quality. We explore these reactions through gas-liquid scattering experiments in vacuum using salty and surfactant-coated glycerol (a low vapor pressure liquid) as a proxy for SSA. HNO$_{3}$ and N$_{2}$O$_{5}$ are atmospherically-relevant species that can dissociate and react at or near the surface of a protic liquid. In particular, N$_{2}$O$_{5}$ may react with the solvent to generate HNO$_{3}$ and glycerol nitrate and may react with near-interfacial Cl$^{-}$ to generate ClNO$_{2}$, Cl$_{2}$, and HONO. Our initial experiments will focus on reactions of DNO$_{3}$ to monitor the competition between HCl and HNO$_{3}$ formation and desorption. [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