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 D17: Disorder and Fluctuations in Chemical Physics IIFocus
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Sponsoring Units: DCP Chair: Rakesh Singh, IISER Tirupati Room: Room 209 |
Monday, March 6, 2023 3:00PM - 3:36PM |
D17.00001: Understanding regulation of CaCO3 crystallization by de novo designed proteins through in situ imaging and spectroscopy Invited Speaker: James J De Yoreo We investigate CaCO3 nucleation in the presence of designed proteins presenting arrays of carboxylate groups in patterns expected to mimic the patterns of calcium sites on various faces of the CaCO3 polymorphs. We combine liquid-phase TEM, liquid and solid state NMR, in situ ATR-FTIR, and molecular modeling to follow the structural and chemical evolution. At moderate supersaturations, the proteins form supramolecular complexes with Ca that drive nucleation of ~3.3 nm calcite, by-passing the amorphous phase observed in pure solution. The initially formed nanocrystals then undergo oriented attachment (OA) to form larger crystals with (110) facets, stabilized by the dissolved proteins. At high supersaturations, the proteins stabilize a viscous dense liquid phase (DLP) that forms by spinodal decomposition and is comprised of 1Ca2+:2HCO3-:7±2H2O. The DLP transforms to hollow particles of hydrated amorphous CaCO3 with the release of CO2 and H2O. NMR shows that the same pathway also occurs in pure solution, but the time scales of formation and transformation differ significantly. Molecular simulations indicate that DLP forms via direct condensation of solvated Ca2+•(HCO3-)2 complexes that react due to proximity effects in the confinement of the DLP droplets to form CaCO3, CO2 and H2O. |
Monday, March 6, 2023 3:36PM - 3:48PM |
D17.00002: Resolving Interfacial Electrochemical Environment from Constrained Optimization Yizhi Shen, Dylan Suvlu, Adam P Willard Madelung potential, or electrostatic potential felt by a given charged species, reports the Coulombic solvation around the host species in electrochemical systems. Fluctuations of the Madelung potential are thus a direct indictor of the structural-dynamical changes from charge reordering phenomena such as layering and screening. For nanoscale systems, a major challenge in the atomistic sampling of Madelung potential is that these potentials are spatially discrete and located sparsely in the electrochemical cell, especially with dilute electrolytes. This makes it difficult to exploit field-theoretic tools to characterize relevant spatial-temporal correlations. In this talk, we present a simple inferential approach to compute a continuous representation of the Madelung potential. Borrowing tools from classical differential geometry, we develop a compact workflow to feed molecular data, as both interior and boundary constraints, into an optimizer that allows the efficient construction of continuous Madelung potential surfaces. Fluctuations in the resulting potential profiles can be post-processed with canonical correlation analysis, revealing the emergence of species-specific interfacial driving forces. |
Monday, March 6, 2023 3:48PM - 4:00PM |
D17.00003: Probing Ca2+ solvation dynamics at the electrolyte/electrode interface Feipeng Yang, Yang Ha, Kun Qian, Scott A McClary, Mesfin Tsige, Kevin R Zavadil, Jinghua Guo Calcium is considered a promising candidate in multivalent beyond lithium-ion batteries because of its safe, economic, and nontoxic nature. It offers a two-fold increase in volumetric capacity compared to monovalent lithium-ion batteries. A systematic understanding of the solvation mechanism and charge transfer at the electrolyte/electrode interface and factors that will affect the solvation is critical in the development of novel calcium batteries. To probe the Ca2+ coordination at the electrolyte/electrode interface as a function of the type of anions, total electron yield (TEY) mode soft X-ray absorption spectroscopy (XAS) sensitive to the interfacial speciation has been employed under in-situ and operando conditions. Meanwhile, total fluorescence yield (TFY) mode XAS is sensitive to bulk speciation. Calcium bis(trifluoromethanesulfonyl)imide (CaTFSI2) in tetrahydrofuran (THF) was selected as an attractive electrolyte because of its oxidative stability and high solubility in various solvents. Combining calcium L-edge soft XAS with resonant soft X-ray scattering (RSoXS) through a patterned interface, the solvation and desolvation dynamics of calcium at the interface were investigated, and the influence of a second cation and anion was investigated. These in-situ/operando synchrotron-based spectroscopic and scattering characterization provide a key to the fundamental mechanisms regarding the solvation and charge transfer at the electrode/electrolyte interface and will benefit the future development of novel energy storage devices. |
Monday, March 6, 2023 4:00PM - 4:36PM |
D17.00004: Transport in fluctuating supercooled and glassy nanoparticle matrices Invited Speaker: Jacinta C Conrad Confined transport within slowly relaxing and structurally disordered matrices governs important processes in physical and biological systems, including polymer nanocomposites, membrane separations, and migration within crowded cells. Anomalous transport often arises in these settings from the competition between the multiscale relaxations of the disordered matrix and the dynamics of the confined particles. This competition depends on both the structure of the matrix and the nature of its relaxations. The connection between matrix relaxations and penetrant transport properties, however, remains incompletely understood despite the strong relevance for many physical transport processes. Here, I will describe experimental and computational studies probing how bulk confinement and matrix relaxations modulate the transport of tracer particles in supercooled or glassy nanoparticle matrices. These studies explore how fluctuations arising either from local rearrangements (due to cage-breaking) or long-wavelength modes (which become more pronounced as systems are increasingly confined towards two dimensions) can alter the particle dynamics and their ability to explore space. |
Monday, March 6, 2023 4:36PM - 4:48PM |
D17.00005: NMR test for glass-freezing dynamics in NiTi strain-glass materials rui li, Jacob Santiago, Joseph H Ross, Jr., Daniel Salas, Woohyun Cho, Ibrahim Karaman We studied Ni50+xTi50-x with compositions between x = 0.1 and 2.0, by performing 47Ti and 49Ti nuclear magnetic resonance (NMR) measurements over a temperature range from 4 K to 400 K. Substitutional disorder has been shown to interrupt the displacive phase transition in these materials and induce a reversible freezing process akin to that of spin glasses or relaxor ferroelectrics. The unfrozen state is characterized by cooperative nanoscale dynamical displacements. Our work probes the local dynamics of this system by NMR spin-lattice relaxation time (T1) measurements, and points to large fluctuation in the parent system as well as in the substituted strain glasses. The Vogel-Fulcher relation has been extensively used to parameterize the relaxation dynamics in glassy systems. However, our results point instead to more standard Arrhenius behavior, implying a nonstandard glass freezing process. High-resolution x-ray measurements indicate no change in the structure across the freezing transition in our samples, even though changes in the NMR shifts show the local difference in electronic behavior. This implies the importance of the distribution of local dynamical behavior in the response of these materials. |
Monday, March 6, 2023 4:48PM - 5:00PM |
D17.00006: Electrostatic potential fluctuations and electron transfer kinetics of gold nanoparticles in aqueous solution Dylan Suvlu, Adam P Willard We have implemented a semi-classical simulation method to calculate the charge distribution within a metal nanoparticle. We have used this method to determine electron transfer rates from gold nanoparticles in aqueous solution with the number of gold atoms ranging from 13 to 561. Our simulation results demonstrate that as the nanoparticle decreases in size, the fluctuations in electrostatic potential and the vertical energy gap increase, subsequently causing an increase in the electron transfer rate. Our results highlight the role of molecular-scale fluctuations in chemical reactivity and will be of general interest to researchers studying heterogeneous catalysis. |
Monday, March 6, 2023 5:00PM - 5:12PM |
D17.00007: A machine learning route to identify the shape of metal nanoparticles Franck Jolibois, Romuald Poteau, Timothée Fages The global structure of nanomaterials can directly influence their physical and chemical properties. Among them catalytic properties depend on the size and shape, as well as on the local structure and environment of catalytic sites. Given the structural versatility of metal NPs as a function of synthesis conditions, the experimental shape recognition of nanoparticles is key. On the way to an automatic classification of the metal core of inorganic NPs from experimental data, a supervised machine learning model trained from numerical simulations was designed. |
Monday, March 6, 2023 5:12PM - 5:24PM |
D17.00008: Multi-step Nucleation in Supersaturated Salt Solutions Using Soft Matter Electrostatic Levitator with In-situ Scattering Techniques John J Lee, Sai C Katamreddy, Hyung-Cheol Lee, Yong Chan Cho, Sooheyong Lee, Geun Woo Lee, Chris Benmore, Matthias D Frontzek, Lisa M DeBeer-Schmitt, Dante G Quirinale, Takeshi Egami For more than a century, nucleation has been viewed as a single-step process as described by classical nucleation theory. With advancements in characterization techniques, complex nucleation mechanisms via intermediate species larger than simple monomeric units have been observed in proteins, colloids, electrolytes, and biominerals. However, the stochastic nature of nucleation at the (sub) nanoscale level makes it challenging to characterize the intermediate phases and interpret their role in complex nucleation. This work aims at understanding the mechanism of complex nucleation in aqueous sodium and magnesium sulfate solutions using a Soft matter Electrostatic Levitator (SEL). 2-3 mm sized droplets were levitated in ambient air in the SEL and supersaturation was achieved by evaporation of water. Changes in solution structure at the molecular level were monitored via in-situ Raman spectroscopy from undersaturation up to nucleation. OH-stretch spectra of water showed the presence of large clusters in supersaturated sodium sulfate solution. Multi-step and concentration-dependent crystallization pathways were observed in both the salts revealing that the solution structure influences the nucleation phase. Crystal microstructure varied depending on the crystallization pathway. The SEL will be integrated with synchrotron X-ray at Advanced Photon Source in Argonne National Laboratory and neutron scattering at Oak Ridge National Laboratory to identify short-range order in the solution and role of solution structure on crystallization pathway. |
Monday, March 6, 2023 5:24PM - 5:36PM |
D17.00009: Unifying atom-centered descriptions and message-passing machine learning schemes Jigyasa Nigam, Michele Ceriotti Over the last decade, dozens of frameworks have been proposed to incorporate machine-learning (ML) techniques in the atomistic simulation toolbox, and in doing so, they have proven to be extremely successful in accelerating the understanding, design, and characterization of materials. Most of these frameworks can be broadly classified into two groups. On one hand, methods relying on physics-based features to represent the underlying structures can be expressed as hierarchical correlations of an atom-centered density (ACDC) imbued with the translational, permutational, and rotational symmetries of the target. Whereas, the alternative class of methods comprises of deep learning models based on the ideas of message-passing (MP) on an atomistic graph, which have been recently extended to integrate geometric equivariance to afford higher descriptive power. |
Monday, March 6, 2023 5:36PM - 5:48PM |
D17.00010: Understanding Metal Ion Interactions in Solvents Using First-Principles and Machine Learning Interatomic Potentials Julia H Yang, Kyle Bystrom, Boris Kozinsky The transport of metal ions in liquids with extensive hydrogen (H)-bonding networks such as deep eutectic solvents (DESs) are essential to study as they have applications in areas such as critical mineral recovery and redox flow batteries for grid energy storage. In particular, experiments have found that ion transport in DESs is possible without a counterion, necessitating first-principles understanding of the local charge transfer between metal ion and neat solvent, solvation shells, and resultant ion transport. |
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