Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session T02: Surfaces and InterfacesRecordings Available
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Sponsoring Units: DCP Chair: Linn Leppert, Univ of Twente Room: McCormick Place W-175C |
Thursday, March 17, 2022 11:30AM - 11:42AM |
T02.00001: Trivalent ion adsorption onto electrified graphene Amanda J Carr, Sang Soo Lee, Ahmet Uysal A complete understanding of ion behavior and water structure near graphene interfaces is critical toward developing promising graphene technologies, including graphene-based membranes for heavy metal separation efforts. While graphene-water interfaces are interesting to both fundamental and applied efforts, molecular-scale information is generally lacking, as these interfacial regions are difficult to probe. Here, we study yttrium ion adsorption onto electrified graphene surfaces using X-ray crystal truncation rod (CTR) and resonant anomalous X-ray reflectivity (RAXR). Both approaches only consider the liquid-graphene interface, and together provide molecular-level, elementally-specific information about yttrium and water organization near graphene interface. |
Thursday, March 17, 2022 11:42AM - 11:54AM |
T02.00002: Molecular modeling of the adsorption-induced expansion of graphene oxide frameworks with covalently bonded benzene-1,4-diboronic acid Todd Lombardi, Joseph Schaeperkoetter, Alberto Albesa, Carlos Wexler Nanoporous activated carbons (AC) with specific surface areas close to the theoretical limits for graphene (2600 m2/g) and pores ~1 nm in width have interest for gas storage and separation. Generally, adsorbents are assumed rigid, even though they are formed by feeble quasi-2D structures resembling graphene flakes. In 2019, Schaeperkoetter et al. [1] observed swelling of graphene oxide frameworks (GOFs) upon the adsorption of methane and xenon under supercritical conditions, i.e., non-condensing. Here we show the results of extensive molecular dynamics simulations (MD) of methane and xenon in various models of GOF’s: (a) benzene-1,4-diboronic acid (DBA) molecules bonded covalently to graphene on both sides, (b) DBA bonded covalently on one side with van der Waals coupling to the other side, and (c) DBA in fluid phase interacting with various polar groups of graphene oxide. MD interaction parameters are based on ab initio B3LYP Density Functional Theory calculations. Our simulations show a monotonic increase of the interlayer spacing for both CH4 and Xe consistent with the experimental observations [1] only for model (a) with randomly oriented linkers. |
Thursday, March 17, 2022 11:54AM - 12:06PM |
T02.00003: Molecular dynamics simulation of the adsorption of sodium dodecyl sulphate on single walled carbon nanotubes in aqueous solution Corey Valleroy, Eric Anglaret, Lucyna Firlej, Bogdan Kuchta, Michael Roth, Carlos Wexler The separation of carbon nanotubes (CNT) into samples that are monodisperse in diameter and chirality still constitutes a bottleneck for specific applications of this material. According to preliminary experimental results [1], surfactant-assisted separation of CNT is a promising solution of this problem. However, the mechanism for which surfactants help the separation with some specificity, or which surfactants or environmental conditions improve the separation are not yet understood. In this work, we present a multi-ensemble molecular dynamics study of the adsorption of sodium dodecyl sulphate (SDS) on a variety of single walled CNT’s [(m, n) = (6,6), (10,2), (11,0), etc.] in aqueous solution at various temperatures. The adsorption of the dodecyl sulfate anions on the CNT is characterized by their atomic radial distribution with respect to the CNT, distribution of characteristic lengths (radius of gyration), and end-to-end azimuthal angle (which shows the degree of wrapping of the molecule around the CNT). We discuss how these are related to the physical characteristics of the CNT’s in solution. |
Thursday, March 17, 2022 12:06PM - 12:18PM |
T02.00004: Adsorption of Argon-Methane Mixture on Planar Graphite Brice Russell, Aldo D Migone, Saikat Talapatra We report on the adsorption equilibration data for Methane and Argon (Ar & CH4) mixtures on planar graphite. Time evolution of the composition of a gaseous mixture of Argon and Methane in the vapor phase during adsorption on graphite sample at different temperatures as well as at several initial pressures were measured. A correlation between the final composition as a function of temperature and initial starting pressure of the gas mixture will be presented and discussed in the light of recent theoretical findings. |
Thursday, March 17, 2022 12:18PM - 12:30PM |
T02.00005: Effect of surface polar groups in nanoporous carbon on the co-adsorption of methane and carbon dioxide Todd Lombardi, Joshua Miles, Mahmoud Attia, Kenedy Tabah, Carlos Wexler
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Thursday, March 17, 2022 12:30PM - 12:42PM |
T02.00006: The Effects of Ultra-High Vacuum on Surface Contamination Zhen Liu, Youngsup Song, Anoop Rajappan, Evelyn N Wang, Daniel J Preston Ultra-high vacuum (UHV) is essential to many surface characterization techniques and is often employed with the intent of controlling or limiting contamination. However, the effect of UHV on surface contamination is not well-understood, adding error to surface elemental characterization techniques and complicating surface-sensitive manufacturing processes. In this work, we investigated the surface composition of gold samples with different initial levels of contamination under UHV for approximately 24 hours through experiments and physical modeling. Results show that the surface carbon concentration under UHV follows a similar evolution as in ambient air and can be explained by molecular adsorption-desorption competition theory. Pristine gold surfaces adsorbed hydrocarbons over time under UHV, whereas pre-contaminated surfaces lost hydrocarbons by desorption. This work provides quantitative evidence of temporal changes in surface contamination under UHV and highlights routes to mitigate these effects in precise experiments or processes conducted under UHV. |
Thursday, March 17, 2022 12:42PM - 12:54PM |
T02.00007: Towards Utilizing Multimodal Optimization to Search for Strontium Titanate Surface Structures Camden M Duy, Nicholas Cheung, Chaitanya Kolluru, Maria K Chan, Dillon D Fong, Kendra L Letchworth-Weaver Understanding crystalline surface-property relationships is crucial for the advancement and production of new technologies. Diffraction based characterization, such as X-Ray Reflectivity (XRR), probes electron distribution at surfaces, but data inversion is difficult. Computational methods such as Density Functional Theory (DFT) are used to minimize energy, but may not accurately reflect realistic experimental conditions. Our developing software FOXPy computes XRR signals from DFT and permits local optimization to determine low energy surface structures. We further enhance the structure search by joining FOXPy to the Fully Automated from Nanoscale to Atomic Structure from Theory and Experiments (FANTASTX) software to perform global optimization. FANTASTX utilizes machine learning algorithms to minimize an objective function which quantifies the fitness of a structural model using both DFT energy and experimental XRR measurements. We aim to discover a structure that is a global minimum of our objective function, thus providing optimal agreement with both experiment and theory. As an example, we investigate the surface of Strontium Titanate (STO), improving our understanding of how epitaxial growth occurs on this common substrate. |
Thursday, March 17, 2022 12:54PM - 1:06PM |
T02.00008: Numerical methods for the parametrization of the lattice generalized langevin equation: applications to surface desoprtion. Ardavan Farahvash, Mayank Agarwal, Adam P Willard The effect of phonons on a single site within a harmonic lattice may be studied using the generalized Langevin equation (GLE), wherein phononic fluctuations are represented by non-Markovian stochastic force and friction terms. The simplicity of the lattice GLE approach has made it a popular choice in applications to the study of surface-gas interactions. However, the determination of the functional form of the friction kernel, and it's role the desoprtion process, remain open challenges. Here we present numerical methods for the calculation of the friction kernel using data taken from molecular dynamics (MD) simulations. Our methods are advantageous in that they may be applied to study the effects of heterogenities, such as surface clusters or defects, as well as the effects of solvents. Results are shown for homogenuous Pt(III) surfaces of various sizes, in vacuum and in water, as well as Au nanoclusters. Finally, we benchmark the GLE models against atomistic MD simulations in the calculation of surface desoprtion rates. |
Thursday, March 17, 2022 1:06PM - 1:18PM Withdrawn |
T02.00009: A multiscale approach towards additive discovery for natural gas hydrate inhibition and promotion Fernanda C Bononi, Oliviero Andreussi Research on natural gas hydrates (NGHs) has witnessed significant contribution in the recent years due to their strong impact on the oil industry, gas storage and environmental science. Particular attention has been devoted to the discovery and design of molecular additives, which can prevent NGHs build-up, the main cause of pipeline blockage. Classical molecular dynamics (MD) simulations of NGHs-additive interactions have allowed for the rationalization of the atomist details that control NGHs formation or inhibition. However, systematic screening and design of molecular additives is hindered by the empirical nature of classical force fields and the costs of free energy calculations. Here we propose a new unbiased approach to investigate NGHs-additive interactions based on a combination of multiscale techniques. Classical MD simulation data is used to generate realistic NGHs interfaces and binding sites. First-principles-based multiscale calculations, combining density and continuum embedding models are then exploited to characterize additive binding energies. Preliminary results from the characterization of quaternary ammonium salts, a class of molecular additives, on the hydrate surface in solutions of 0 and 100% watercut will be presented. |
Thursday, March 17, 2022 1:18PM - 1:30PM |
T02.00010: Visualization of Sn Adsorption and Diffusion Behavior on (3×1)-O/Nb(100) with Low and Moderate Defect Densities Rachael G Farber, Sarah A Willson, Steven J Sibener Nb3Sn is a promising next-generation material for superconducting radio frequency (SRF) cavities, but a mechanistic understanding of optimal Nb3Sn film growth has not been realized; this is needed to achieve optimized alloy growth for high-performance Nb3Sn SRF cavities. Using in situ ultra-high vacuum surface preparation and characterization techniques, Sn adsorption and diffusion behavior was visualized at the nanoscale on a low (ρL) and moderate (ρM) defect density (3×1)-O/Nb(100) surface. Scanning tunneling microscopy data revealed distinct Sn adsorption behavior at room temperature on pristine, ρL, and ρM surfaces. Elevated surface temperatures induced Sn diffusion pathways primarily guided by the underlying oxide structure. The ρM surface displayed enhanced Sn thermal stability, highlighting the role of structural defects in stabilizing adsorbed Sn species at elevated temperatures. Auger electron spectroscopy showed consistent surface composition of the ρL and ρM substrates, suggesting that surface and near-surface composition is not influenced by nanoscale defects. This work provides the first in situ nanoscale visualization of Sn adsorption and diffusion on oxidized Nb and illustrates the significance of the underlying Nb oxide morphology on Sn adsorption and diffusion. |
Thursday, March 17, 2022 1:30PM - 1:42PM |
T02.00011: CO vibrational frequencies as probe of Pt local environment in Pt1/CeO2 single atom catalysts: First principles investigations Dave Austin, Duy Le, Shaohua Xie, Sampyo Hong, Fudong Liu, Talat S Rahman Singly dispersed Pt atoms on CeO2 surfaces (Pt1/CeO2) have been proposed as effective catalysts for several reactions. Knowledge of the local environment of the Pt atom that would enable rational design of the catalyst is still under debate. Under ambient conditions, experimental information on the local atomic geometry of the catalyst relies on the observed vibrational frequencies of adsorbates. Using density functional theory, we have examined the adsorption and vibrational characteristics of CO on Pt1/CeO2 in the presences of vacancies, step edges, terraces of CeO2(111) and CeO2(110) with the aim to build a vibrational-signature database. We find that the stretching frequency of the CO molecule adsorbed at Pt atoms depends strongly on the coordination of Pt to neighboring O atoms, i.e., higher such coordination results in higher stretching frequency. Such dependence is not clearly seen for the coordination of Pt to neighboring Ce atoms. The database of CO vibrational frequencies together with possible local environment descriptor are used to interpret experimental data taken in this joint theoretical and experimental collaboration from which the nature of the single Pt atom site or ceria is identified. |
Thursday, March 17, 2022 1:42PM - 1:54PM |
T02.00012: When does surface polymorphism matter for the work function of organic/metal interfaces? Andreas Jeindl, Lukas Hörmann, Oliver T Hofmann
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Thursday, March 17, 2022 1:54PM - 2:06PM |
T02.00013: The structure of water at interfaces through ab initio simulations of non-linear spectroscopy Alan M Lewis, Paolo Lazzaroni, Mariana Rossi Hydrogen evolution through heterogeneous catalysis is an increasingly widespread method of storing energy generated from renewable sources, and as such is becoming a central part of green energy grids. Understanding the structure of water at solid surfaces is vital to find more efficient and cost-effective catalysts of this reaction, and sum-frequency generation spectroscopy provides a surface-specific method of investigating these structures.[1] We present a new framework for ab initio calculations of the sum-frequency response of water-solid interfaces, avoiding the need for an arbitrary molecular decomposition of the polarizability and dipole moment of the system by evaluating these quantities using real space integrals.[2] This allows us to investigate the effect of this decomposition on the sum-frequency response of the much-studied water/vacuum interface. This approach also enables us to account explicitly for the contribution of the solid to the polarizability and dipole moment of the interface, which are commonly neglected. We demonstrate the impact of these contributions on the sum-frequency response of water/metal oxide interfaces. |
Thursday, March 17, 2022 2:06PM - 2:18PM |
T02.00014: Fully Atomistic Modeling of Carbon Quantum Dots in Aqueous Solution Clarisse Basset, Bogdan Kuchta, Lucyna Firlej, Michael Roth, Carlos Wexler We present the results of extensive multiensemble Molecular Dynamics simulations of triangular Graphene Quantum Dots (GQD’s) solvated in water at room temperature. We use energetics, structural quantities and autocorrelation functions in three different ensembles to provide insight into the nature of the behavior of systems comprised of 2 to 6 triangular graphene-like layers for both armchair (AM) and zigzag (ZZ) configurations of 54 to 168 carbon and 27 to 42 hydrogen atoms per layer. The individual layers remain very rigid even for the largest layers and there is a small amount of inter-layer spacing variation between different systems. Simulated Raman spectra capture a wide variety of normal modes in the system that are highly dependent on the structure under consideration, suggesting that Raman spectra can be used to experimentally distinguish between these. Results are in reasonable agreement with those calculated and observed in multilayer graphene systems. |
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