123 results on '"Enrique R. Batista"'
Search Results
2. Architector for high-throughput cross-periodic table 3D complex building
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Michael G. Taylor, Daniel J. Burrill, Jan Janssen, Enrique R. Batista, Danny Perez, and Ping Yang
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Science - Abstract
Abstract Rare-earth and actinide complexes are critical for a wealth of clean-energy applications. Three-dimensional (3D) structural generation and prediction for these organometallic systems remains a challenge, limiting opportunities for computational chemical discovery. Here, we introduce Architector, a high-throughput in-silico synthesis code for s-, p-, d-, and f-block mononuclear organometallic complexes capable of capturing nearly the full diversity of the known experimental chemical space. Beyond known chemical space, Architector performs in-silico design of new complexes including any chemically accessible metal-ligand combinations. Architector leverages metal-center symmetry, interatomic force fields, and tight binding methods to build many possible 3D conformers from minimal 2D inputs including metal oxidation and spin state. Over a set of more than 6,000 x-ray diffraction (XRD)-determined complexes spanning the periodic table, we demonstrate quantitative agreement between Architector-predicted and experimentally observed structures. Further, we demonstrate out-of-the box conformer generation and energetic rankings of non-minimum energy conformers produced from Architector, which are critical for exploring potential energy surfaces and training force fields. Overall, Architector represents a transformative step towards cross-periodic table computational design of metal complex chemistry.
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- 2023
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3. Author Correction: Architector for high-throughput cross-periodic table 3D complex building
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Michael G. Taylor, Daniel J. Burrill, Jan Janssen, Enrique R. Batista, Danny Perez, and Ping Yang
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Science - Published
- 2023
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4. N2-to-NH3 conversion by excess electrons trapped in point vacancies on 5f-element dioxide surfaces
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Gaoxue Wang, Enrique R. Batista, and Ping Yang
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N2-to-NH3 conversion ,excess electrons ,point vacancies ,actinide dioxide surfaces ,DFT density functional theory ,Chemistry ,QD1-999 - Abstract
Ammonia (NH3) is one of the basic chemicals in artificial fertilizers and a promising carbon-free energy storage carrier. Its industrial synthesis is typically realized via the Haber−Bosch process using traditional iron-based catalysts. Developing advanced catalysts that can reduce the N2 activation barrier and make NH3 synthesis more efficient is a long-term goal in the field. Most heterogeneous catalysts for N2-to-NH3 conversion are multicomponent systems with singly dispersed metal clusters on supporting materials to activate N2 and H2 molecules. Herein, we report single-component heterogeneous catalysts based on 5f actinide dioxide surfaces (ThO2 and UO2) with oxygen vacancies for N2-to-NH3 conversion. The reaction cycle we propose is enabled by a dual-site mechanism, where N2 and H2 can be activated at different vacancy sites on the same surface; NH3 is subsequently formed by H− migration on the surface via associative pathways. Oxygen vacancies recover to their initial states after the release of two molecules of NH3, making it possible for the catalytic cycle to continue. Our work demonstrates the catalytic activities of oxygen vacancies on 5f actinide dioxide surfaces for N2 activation, which may inspire the search for highly efficient, single-component catalysts that are easy to synthesize and control for NH3 conversion.
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- 2023
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5. δ and φ back-donation in AnIV metallacycles
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Morgan P. Kelley, Ivan A. Popov, Julie Jung, Enrique R. Batista, and Ping Yang
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Science - Abstract
Metal-ligand δ and φ interactions, though considered weak, may be necessary for fully describing the electronic and geometric structures of certain compounds. Here, in actinide metallacycles, the authors discover two new types of M-L δ and φ back-bonds that contribute substantially to their unusual chemical behavior.
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- 2020
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6. Impact of Ligand Substitutions on Multielectron Redox Properties of Fe Complexes Supported by Nitrogenous Chelates
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Ivan A. Popov, Nada Mehio, Terry Chu, Benjamin L. Davis, Rangachary Mukundan, Ping Yang, and Enrique R. Batista
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Chemistry ,QD1-999 - Published
- 2018
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7. Synthesis and Characterization of the Actinium Aquo Ion
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Maryline G. Ferrier, Benjamin W. Stein, Enrique R. Batista, John M. Berg, Eva R. Birnbaum, Jonathan W. Engle, Kevin D. John, Stosh A. Kozimor, Juan S. Lezama Pacheco, and Lindsay N. Redman
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Chemistry ,QD1-999 - Published
- 2017
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8. Catalyst-Inspired Charge Carriers for High Energy Density Redox Flow Batteries
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Ivan A. Popov, Benjamin L. Davis, Rangachary Mukundan, Enrique R. Batista, and Ping Yang
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redox flow batteries (RFB) ,catalyst-inspired ,computational modeling ,density functional theory ,Fe-complex ,redox potentials ,Physics ,QC1-999 - Abstract
We introduce a theoretical design approach aiming at improving energy density of redox flow batteries (RFBs) via the utilization of redox non-innocent ligands capable of stabilizing a metal center in a wide range of oxidation states. Our findings suggest that this promotes the possibility of multiple redox events as well as high open circuit voltages. Specifically, we have proposed two Fe-coordination complexes (I, Fe(Me2Pytacn)(C2N3H2), and II, Fe(H2pmen)(C2N3H2)) combining two different types of ligands, i.e., catalyst-inspired scaffolds and triazole ring, which were previously shown to promote high and low oxidation states in transition metals, respectively. These complexes exhibit as many as six theoretical redox events in the full range of charge states +4 → −2, several of which reside within the electrochemical window of acetonitrile. Electronic structure calculations show that the Fe center exhibits oxidation states ranging from the very rare Fe4+ to Fe1+. Values of the reduction potentials as well as nature of the redox events of both complexes is found to be similar in their high +4 → +1 charge states. In contrast, while exhibiting qualitatively similar redox behavior in the lower 0 → −2 range, some differences in the electronic ground states, delocalization patterns as well as reduction potential values are also observed. The calculated open circuit voltages can reach values of 5.09 and 6.14 V for complexes I and II, respectively, and hold promise to be experimentally accessible within the electrochemical window of acetonitrile expanded by addition of ionic liquids. The current results obtained for these two complexes are intended to illustrate a more general principle based on the simultaneous utilization of two types of ligands responsible for the stabilization of high and low oxidation states of the metal that can be used to design the next-generation charge carriers capable of supporting multi-electron redox and operating in a broad range of charge states, leading to RFBs with greater energy density.
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- 2019
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9. Spectroscopic and computational investigation of actinium coordination chemistry
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Maryline G. Ferrier, Enrique R. Batista, John M. Berg, Eva R. Birnbaum, Justin N. Cross, Jonathan W. Engle, Henry S. La Pierre, Stosh A. Kozimor, Juan S. Lezama Pacheco, Benjamin W. Stein, S. Chantal E. Stieber, and Justin J. Wilson
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Science - Abstract
Actinium-225 is a promising isotope for α-therapy but progress in developing its chemistry is hindered by its high radioactivity and short supply. Here, the authors characterize actinium coordination in HCl solutions using X-ray absorption spectroscopy and molecular dynamics density functional theory.
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- 2016
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10. Water on Actinide Dioxide Surfaces: A Review of Recent Progress
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Gaoxue Wang, Enrique R. Batista, and Ping Yang
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actinide dioxide ,surface chemistry ,water splitting ,density functional theory ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The fluorite structured actinide dioxides (AnO2), especially UO2, are the most common nuclear fuel materials. A comprehensive understanding of their surface chemistry is critical because of its relevance to the safe handling, usage, and storage of nuclear fuels. Because of the ubiquitous nature of water (H2O), its interaction with AnO2 has attracted significant attention for its significance in studies of nuclear fuels corrosion and the long-term storage of nuclear wastes. The last few years have seen extensive experimental and theoretical studies on the H2O–AnO2 interaction. Herein, we present a brief review of recent advances in this area. We focus on the atomic structures of AnO2 surfaces, the surface energies, surface oxygen vacancies, their influence on the oxidation states of actinide atoms, and the adsorption and reactions of H2O on stoichiometric and reduced AnO2 surfaces. Finally, a summary and outlook of future studies on surface chemistry of AnO2 are given. We intend for this review to encourage broader interests and further studies on AnO2 surfaces.
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- 2020
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11. Kinetics of alkali-based photocathode degradation
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Vitaly Pavlenko, Fangze Liu, Mark A. Hoffbauer, Nathan A. Moody, and Enrique R. Batista
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Physics ,QC1-999 - Abstract
We report on a kinetic model that describes the degradation of the quantum efficiency (QE) of Cs3Sb and negative electron affinity (NEA) GaAs photocathodes under UHV conditions. In addition to the generally accepted irreversible chemical change of a photocathode’s surface due to reactions with residual gases, such as O2, CO2, and H2O, the model incorporates an intermediate reversible physisorption step, similar to Langmuir adsorption. This intermediate step is needed to satisfactorily describe the strongly non-exponential QE degradation curves for two distinctly different classes of photocathodes –surface-activated and “bulk,” indicating that in both systems the QE degradation results from surface damage. The recovery of the QE upon improvement of vacuum conditions is also accurately predicted by this model with three parameters (rates of gas adsorption, desorption, and irreversible chemical reaction with the surface) comprising metrics to better characterize the lifetime of the cathodes, instead of time-pressure exposure expressed in Langmuir units.
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- 2016
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12. State Interaction Linear Response Time-Dependent Density Functional Theory with Perturbative Spin–Orbit Coupling: Benchmark and Perspectives
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Can Liao, Joseph M. Kasper, Andrew J. Jenkins, Ping Yang, Enrique R. Batista, Michael J. Frisch, and Xiaosong Li
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- 2023
13. Relativistic Effects in Modeling the Ligand K-Edge X-ray Absorption Near-Edge Structure of Uranium Complexes
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Joseph M. Kasper, Xiaosong Li, Stosh A. Kozimor, Enrique R. Batista, and Ping Yang
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Physical and Theoretical Chemistry ,Computer Science Applications - Abstract
Accurate modeling of the complex electronic structure of actinide complexes requires full inclusion of relativistic effects. In this study, we examine the effect of explicit inclusion of spin-orbit coupling (SOC) versus scalar relativistic effects on the predicted spectra for heavy-element complexes. In this study, we employ a relativistic two-component Hamiltonian in the X2C form with all of the electrons in the system being considered explicitly to compare and contrast with previous studies that included the relativistic effects by means of relativistic effective core potentials (RECPs). A few uranium complexes are chosen as model systems. Comparison of the computed Cl K-edge X-ray absorption spectra with experimental data shows significantly improved agreement when a variational relativistic treatment of SOC is performed. In particular, we note the importance of SOC terms to obtain not only correct transition energies but also correct intensities for these heavy-element complexes because of the redistribution of ligand bonding character among the valence MOs. While RECPs generally agree well with all-electron scalar relativistic calculations, there are some differences in the predicted spectra of open-shell systems. These methods are still suitable for broad application to analyze the qualitative nature of transitions in X-ray absorption spectra, but caution is recommended for quantitative analysis, as SOC can be non-negligible for both open- and closed-shell heavy-element systems.
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- 2022
14. Pairwise Difference Regression: A Machine Learning Meta-algorithm for Improved Prediction and Uncertainty Quantification in Chemical Search
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Michael Tynes, Enrique R. Batista, Daniel Burrill, Wenhao Gao, Ping Yang, Nicholas Lubbers, and Danny Perez
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Artificial neural network ,Computer science ,business.industry ,Active learning (machine learning) ,General Chemical Engineering ,Uncertainty ,General Chemistry ,Library and Information Sciences ,Machine learning ,computer.software_genre ,Regression ,Computer Science Applications ,Random forest ,Machine Learning ,Data point ,Errors-in-variables models ,Pairwise comparison ,Neural Networks, Computer ,Artificial intelligence ,Uncertainty quantification ,business ,Algorithm ,computer ,Algorithms - Abstract
Machine learning (ML) plays a growing role in the design and discovery of chemicals, aiming to reduce the need to perform expensive experiments and simulations. ML for such applications is promising but difficult, as models must generalize to vast chemical spaces from small training sets and must have reliable uncertainty quantification metrics to identify and prioritize unexplored regions. Ab initio computational chemistry and chemical intuition alike often take advantage of differences between chemical conditions, rather than their absolute structure or state, to generate more reliable results. We have developed an analogous comparison-based approach for ML regression, called pairwise difference regression (PADRE), which is applicable to arbitrary underlying learning models and operates on pairs of input data points. During training, the model learns to predict differences between all possible pairs of input points. During prediction, the test points are paired with all training set points, giving rise to a set of predictions that can be treated as a distribution of which the mean is treated as a final prediction and the dispersion is treated as an uncertainty measure. Pairwise difference regression was shown to reliably improve the performance of the random forest algorithm across five chemical ML tasks. Additionally, the pair-derived dispersion is both well correlated with model error and performs well in active learning. We also show that this method is competitive with state-of-the-art neural network techniques. Thus, pairwise difference regression is a promising tool for candidate selection algorithms used in chemical discovery.
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- 2021
15. Hyperspectral X-Ray Imaging: Progress Towards Chemical Analysis in the SEM
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Ping Yang, Katrina Koehler, Eric G. Bowes, Enrique R. Batista, Gene C. Hilton, M. H. Carpenter, Carl D. Reintsema, Douglas A. Bennett, Daikang Yan, Johnathon D. Gard, Zachary K. Baker, Daniel S. Swetz, Michael W. Rabin, M. P. Croce, Katherine A. Schreiber, Gregory L. Wagner, Joel C. Weber, Daniel T. Becker, Daniel Schmidt, Benjamin W. Stein, Chandler M. Smith, Christopher J. Fontes, Galen C. O'Neil, Abigail L. Wessels, Joel N. Ullom, Matthew L. Handley, J. Imrek, Kelsey M. Morgan, John A. B. Mates, and Daniel G. McNeel
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Cryostat ,Materials science ,Pixel ,Scanning electron microscope ,business.industry ,Detector ,Hyperspectral imaging ,Condensed Matter Physics ,01 natural sciences ,Sample (graphics) ,Electronic, Optical and Magnetic Materials ,Chemical species ,Optics ,0103 physical sciences ,Electrical and Electronic Engineering ,010306 general physics ,business ,Microwave - Abstract
The Hyperspectral X-ray Imaging (HXI) project will enable non-destructive chemical-state determination of nano-scale samples in the electron microscope for nuclear safeguards applications. To efficiently measure chemical state through electron-excited X-ray emission requires a combination of wide spectral bandwidth, high resolution, and high count rate capability. We are building a next-generation X-ray detector based on an array of transition edge sensors (TESs) to make these measurements possible and routine in the scanning electron microscope (SEM). Leveraging the large pixel densities afforded by microwave multiplexing readout and continuous, uninterrupted operation of a cryogen-free dilution refrigerator, this instrument will have efficiency to allow chemical species identification of nano-scale samples in hours instead of days to weeks. We describe prototype pixel designs for this HXI instrument, comprising three pixel types that will make up the hybrid TES array. Engineering design of the integrated HXI cryostat and SEM system is in progress, with full detector commissioning expected in Spring 2021 followed closely by full-scale integration with the SEM. We also report on the commissioning of a complementary TES-based X-ray emission spectroscopy platform for bulk samples to build a spectral library for HXI sample identification.
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- 2021
16. Hydrazine Energy Storage: Displacing N 2 H 4 from the Metal Coordination Sphere
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Andrew J. McNeece, Adam Jaroš, Enrique R. Batista, Ping Yang, Brian L. Scott, and Benjamin L. Davis
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General Energy ,General Chemical Engineering ,Environmental Chemistry ,General Materials Science - Published
- 2022
17. High Resolution X-Ray Spectra for Chemical Speciation in the SEM
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Eric G. Bowes, Lei Xu, Chandler M. Smith, Michael W. Rabin, Enrique R. Batista, Benjamin W. Stein, M. P. Croce, Katherine A. Schreiber, M. H. Carpenter, Christopher J. Fontes, Katrina Koehler, Daniel G. McNeel, Gregory L. Wagner, and Ping Yang
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Materials science ,Chemical speciation ,Analytical chemistry ,High resolution ,Instrumentation ,X ray spectra - Published
- 2021
18. Iron-iminopyridine complexes as charge carriers for non-aqueous redox flow battery applications
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Ivan A. Popov, Benjamin L. Davis, Aaron M. Tondreau, Ping Yang, Enrique R. Batista, Gabriel A. Andrade, Shikha Sharma, John C. Gordon, Sandip Maurya, Nathan C. Smythe, and Rangachary Mukundan
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Aqueous solution ,Materials science ,Renewable Energy, Sustainability and the Environment ,Energy Engineering and Power Technology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Combinatorial chemistry ,Flow battery ,Redox ,Energy storage ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,General Materials Science ,0210 nano-technology ,Acetonitrile ,Faraday efficiency ,Diimine - Abstract
Non-aqueous redox flow batteries (RFBs) have been gaining increased attention in the energy storage arena. Some of their attractive features include the promise for high energy densities, wider voltage windows compared to aqueous systems, as well as wider operating temperature ranges. One of the major challenges in the development of these systems is the lack of electroactive materials that can undergo reversible redox events within the larger potential window of organic solvents. Herein, we present the design, synthesis, and measurement of electrochemical properties of some iron-based imine- and iminopyridine complexes as promising candidates for RFB applications. Synthesized complexes afforded three reversible redox couples over a ~3 V range. The redox events were also computationally explored and are in good agreement with experimental data. Theoretical calculations show that the redox event at the positive potential can be characterized as metal-centered event corresponding to Fe3+→ Fe2+ reduction, while the two redox events at negative potentials are associated with the consecutive reductions of iminopyridine or diimine moieties. This work has led to the identification of a promising anolyte material, [tris(imino)pyridine)Fe][OTf]2 (1), which is soluble in acetonitrile and is synthesized in two simple steps. This species shows outstanding performance when cycled between 1.0 V and 2.35 V, with 93% coulombic efficiency, 84% energy efficiency, and a capacity decay rate of 0.61% per cycle at 5 mA cm−2. Further modifications to this kind of charge carrier may lead to the development of high energy density materials for grid scale energy storage applications.
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- 2021
19. Synthesis, solid-state, solution, and theoretical characterization of an 'in-cage' scandium-NOTA complex
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Kelly E. Aldrich, Ivan A. Popov, Harrison D. Root, Enrique R. Batista, Samuel M. Greer, Stosh A. Kozimor, Laura M. Lilley, Maksim Y. Livshits, Veronika Mocko, Michael T. Janicke, Brian L. Scott, Benjamin W. Stein, and Ping Yang
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Inorganic Chemistry ,Heterocyclic Compounds, 1-Ring ,Ligands ,Scandium ,Chelating Agents - Abstract
Developing chelators that strongly and selectively bind rare-earth elements (Sc, Y, La, and lanthanides) represents a longstanding fundamental challenge in inorganic chemistry. Solving these challenges is becoming more important because of increasing use of rare-earth elements in numerous technologies, ranging from paramagnets to luminescent materials. Within this context, we interrogated the complexation chemistry of the scandium(III) (Sc
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- 2022
20. Structural and Spectroscopic Comparison of Soft‐Se vs. Hard‐O Donor Bonding in Trivalent Americium/Neodymium Molecules
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Conrad A. P. Goodwin, Anthony W. Schlimgen, Thomas E. Albrecht‐Schönzart, Enrique R. Batista, Andrew J. Gaunt, Michael T. Janicke, Stosh A. Kozimor, Brian L. Scott, Lauren M. Stevens, Frankie D. White, and Ping Yang
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010405 organic chemistry ,chemistry.chemical_element ,Americium ,General Medicine ,General Chemistry ,Actinide ,010402 general chemistry ,01 natural sciences ,Neodymium ,Catalysis ,0104 chemical sciences ,Crystallography ,chemistry ,Ab initio quantum chemistry methods ,Covalent bond ,Molecule ,Spectroscopy ,Selectivity - Abstract
Covalency is often considered to be an influential factor in driving An3+ vs. Ln3+ selectivity invoked by soft donor ligands. This is intensely debated, particularly the extent to which An3+ /Ln3+ covalency differences prevail and manifest as the f-block is traversed, and the effects of periodic breaks beyond Pu. Herein, two Am complexes, [Am{N(E=PPh2 )2 }3 ] (1-Am, E=Se; 2-Am, E=O) are compared to isoradial [Nd{N(E=PPh2 )2 }3 ] (1-Nd, 2-Nd) complexes. Covalent contributions are assessed and compared to U/La and Pu/Ce analogues. Through ab initio calculations grounded in UV-vis-NIR spectroscopy and single-crystal X-ray structures, we observe differences in f orbital involvement between Am-Se and Nd-Se bonds, which are not present in O-donor congeners.
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- 2021
21. Structural and Optical Properties of Phase-Pure UO2, α-U3O8, and α-UO3 Epitaxial Thin Films Grown by Pulsed Laser Deposition
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Quanxi Jia, Joshua T. White, J.T. Dunwoody, Xiaofeng Guo, Erik Enriquez, Hongwu Xu, Andrew T. Nelson, Ping Yang, Yogesh Sharma, Nicholas Winner, Aiping Chen, Ibrahim Sarpkaya, Qiang Wang, Paul Dowden, Enrique R. Batista, Han Htoon, Gaoxue Wang, and Di Chen
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Materials science ,010405 organic chemistry ,business.industry ,Epitaxial thin film ,chemistry.chemical_element ,Uranium ,010402 general chemistry ,Epitaxy ,01 natural sciences ,0104 chemical sciences ,Pulsed laser deposition ,chemistry ,Phase (matter) ,Optoelectronics ,General Materials Science ,Thin film ,business - Abstract
Fundamental understanding of the electronic, chemical, and structural properties of uranium oxides requires the synthesis of high-crystalline-quality epitaxial films of different polymorphs of one ...
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- 2020
22. Hyperspectral X-ray Imaging with TES Detectors for Nanoscale Chemical Speciation Mapping
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J. A. Hall, D. T. Carver, Chris J. Fontes, J. D. Gard, Galen C. O'Neil, Ping Yang, D. T. Becker, Michael Yoho, Enrique R. Batista, Daikang Yan, Michael W. Rabin, Daniel S. Swetz, B. W. Renck, Gregory L. Wagner, Zachary K. Baker, Gene C. Hilton, Katrina Koehler, Kathryn G. McIntosh, Douglas A. Bennett, M. H. Carpenter, Joel N. Ullom, M. P. Croce, M. Caffrey, Carl D. Reintsema, J. Imrek, Marianne P. Wilkerson, Abigail L. Wessels, S. E. Kossmann, R. H. Cantor, Daniel Schmidt, John A. B. Mates, and Kelsey M. Morgan
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Chemical imaging ,Materials science ,Pixel ,business.industry ,Detector ,Hyperspectral imaging ,Condensed Matter Physics ,01 natural sciences ,Multiplexing ,Atomic and Molecular Physics, and Optics ,Synchrotron ,010305 fluids & plasmas ,law.invention ,law ,0103 physical sciences ,Optoelectronics ,General Materials Science ,Transition edge sensor ,010306 general physics ,business ,Microwave - Abstract
We are developing an imaging capability (“Hyperspectral X-ray Imaging”) for mapping chemical information (molecular formula, phase, oxidation state, hydration) that is based on ultra-high-resolution X-ray emission spectroscopy with large transition-edge sensor microcalorimeter arrays in the scanning electron microscope. By combining microcalorimeter arrays with hundreds of pixels, high-bandwidth microwave frequency-division multiplexing, and fast digital electronics for near real-time data processing, our goal is to enable measurements using laboratory-scale instrumentation rather than synchrotron beamlines. Our application focus here is on mapping the chemical form of uranium compounds on the nanoscale. We will present our approach to developing the Hyperspectral X-ray Imaging capability, progress toward a 128-pixel microwave multiplexed X-ray fluorescence instrument at LANL, and the path to high-throughput nanoscale chemical mapping.
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- 2020
23. Expanding the potential of redox carriers for flow battery applications
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Ping Yang, Ivan A. Popov, Gabriel A. Andrade, Benjamin L. Davis, Celia R. Federico, Enrique R. Batista, and Rangachary Mukundan
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Materials science ,Renewable Energy, Sustainability and the Environment ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Redox ,Flow battery ,0104 chemical sciences ,Metal ,chemistry.chemical_compound ,Nickel ,chemistry ,visual_art ,visual_art.visual_art_medium ,Dimethylformamide ,General Materials Science ,Differential pulse voltammetry ,Solubility ,0210 nano-technology ,Acetonitrile - Abstract
Using theoretical modeling to guide our approach, substituents were selected to improve the negative and positive potentials associated with a representative metal-based redox carrier, a phenyl spaced nickel bispicolinamide complex, [Ni(bpb)], 1. To broaden the cell potential, electron donating groups were selected and installed on the pyridyl moieties, [Ni(bpb-(NMe2)2)], 2, while electron withdrawing groups were incorporated on the phenyl linker, [Ni(bpb-R)] (R = –F, –CF3, and –NO2), 3–5. Our model predicts an increase of ∼300 mV and ∼500 mV for the first and second negative waves of Ni(bpb-NMe2), 2, and up to ∼330 mV and ∼210 mV increase to the first and second positive waves in 3–5. The modeled complexes were synthesized in good yields using a modification of the literature procedure. Due to limited solubility, the differential pulse voltammetry was measured on complexes 2–5 using a drop cast technique. Comparison of the observed and predicted potentials is discussed in acetonitrile (MeCN) and dimethylformamide (DMF) solvents.
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- 2020
24. Comparison of tetravalent cerium and terbium ions in a conserved, homoleptic imidophosphorane ligand field
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Henry S. La Pierre, John Bacsa, Ivan A. Popov, Thaige P. Gompa, Enrique R. Batista, Ping Yang, Arun Ramanathan, Dominic R. Russo, and Natalie T. Rice
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Ligand field theory ,Lanthanide ,Crystallography ,chemistry.chemical_compound ,chemistry ,Covalent bond ,Ligand ,chemistry.chemical_element ,Terbium ,General Chemistry ,Homoleptic ,Isostructural ,Natural bond orbital - Abstract
A redox pair of Ce4+ and Ce3+ complexes has been prepared that is stabilized by the [(NP(1,2-bis-tBu-diamidoethane)(NEt2))]1− ligand. Since these complexes are isostructural to the recently reported isovalent terbium analogs, a detailed structural and spectroscopic comparative analysis was pursued via Voronoi–Dirichlet polyhedra analysis, UV-vis-NIR, L3-edge X-ray absorption near edge spectroscopy (XANES), cyclic voltammetry, and natural transitions orbital (NTO) analysis and natural bond orbital (NBO) analysis. The electrochemical studies confirm previous theoretical studies of the redox properties of the related complex [K][Ce3+(NP(pip)3)4] (pip = piperidinyl), 1-Ce(PN). Complex 1-Ce(PN*) presents the most negative Epc of −2.88 V vs. Fc/Fc+ in THF of any cerium complex studied electrochemically. Likewise 1-Tb(PN*) has the most negative Epc for electrochemically interrogated terbium complexes at −1.79 V vs. Fc/Fc+ in THF. Complexes 1-Ce(PN*) and 2-Ce(PN*) were also studied by L3-edge X-ray absorption near edges spectroscopy (XANES) and a comparison to previously reported spectra for 1-Tb(PN*), 2-Tb(PN*), 1-Ce(PN), and, [Ce4+(NP(pip)3)4], 2-Ce(PN), demonstrates similar nf values for all the tetravalent lanthanide complexes. According to the natural bond orbital analysis, a greater covalent character of the M–L bonds is found in 2-Ce(PN*) than in 1-Ce(PN*), in agreement with the shorter Ce–N bonds in the tetravalent counterpart. The greater contribution of Ce orbitals in the Ce–N bonding and, specifically, the higher participation of 4f electrons accounts for the stronger covalent interactions in 2-Ce(PN*) as compared to 2-Tb(PN*).
- Published
- 2020
25. An Allyl Uranium(IV) Sandwich Complex: Are ϕ Bonding Interactions Possible?
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Ivan A. Popov, Brennan S. Billow, Stephanie H. Carpenter, Enrique R. Batista, James M. Boncella, Aaron M. Tondreau, and Ping Yang
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Organic Chemistry ,General Chemistry ,Catalysis - Abstract
A method to explore head-to-head ϕ back-bonding from uranium f-orbitals into allyl π* orbitals has been pursued. Anionic allyl groups were coordinated to uranium with tethered anilide ligands, then the products were investigated by using NMR spectroscopy, single-crystal XRD, and theoretical methods. The (allyl)silylanilide ligand, N-((dimethyl)prop-2-enylsilyl)-2,6-diisopropylaniline (LH), was used as either the fully protonated, singly deprotonated, or doubly deprotonated form, thereby highlighting the stability and versatility of the silylanilide motif. A free, neutral allyl group was observed in UI
- Published
- 2022
26. Isolation and characterization of a californium metallocene
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William J. Evans, Conrad A. P. Goodwin, Joseph M. Sperling, Thomas E. Albrecht-Schönzart, Jing Su, Stosh A. Kozimor, Lauren M. Stevens, Justin C. Wedal, Ping Yang, Frankie D. White, Zachary R. Jones, Sasha F. Briscoe, Alyssa N. Gaiser, Cory J. Windorff, Enrique R. Batista, Andrew J. Gaunt, Joseph W. Ziller, Brian L. Scott, Nickolas H. Anderson, Michael R. James, John D. Auxier, Justin N. Cross, Tener F. Jenkins, and Michael T. Janicke
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chemistry.chemical_compound ,Crystallography ,Multidisciplinary ,Valence (chemistry) ,chemistry ,Chemical bond ,Bent metallocene ,chemistry.chemical_element ,Molecule ,Ionic bonding ,Californium ,Isostructural ,Organometallic chemistry - Abstract
Californium (Cf) is currently the heaviest element accessible above microgram quantities. Cf isotopes impose severe experimental challenges due to their scarcity and radiological hazards. Consequently, chemical secrets ranging from the accessibility of 5f/6d valence orbitals to engage in bonding, the role of spin–orbit coupling in electronic structure, and reactivity patterns compared to other f elements, remain locked. Organometallic molecules were foundational in elucidating periodicity and bonding trends across the periodic table1–3, with a twenty-first-century renaissance of organometallic thorium (Th) through plutonium (Pu) chemistry4–12, and to a smaller extent americium (Am)13, transforming chemical understanding. Yet, analogous curium (Cm) to Cf chemistry has lain dormant since the 1970s. Here, we revive air-/moisture-sensitive Cf chemistry through the synthesis and characterization of [Cf(C5Me4H)2Cl2K(OEt2)]n from two milligrams of 249Cf. This bent metallocene motif, not previously structurally authenticated beyond uranium (U)14,15, contains the first crystallographically characterized Cf–C bond. Analysis suggests the Cf–C bond is largely ionic with a small covalent contribution. Lowered Cf 5f orbital energy versus dysprosium (Dy) 4f in the colourless, isoelectronic and isostructural [Dy(C5Me4H)2Cl2K(OEt2)]n results in an orange Cf compound, contrasting with the light-green colour typically associated with Cf compounds16–22.
- Published
- 2021
27. 'Sweeping' Ortho Substituents Drive Desolvation and Overwhelm Electronic Effects in Nd3+ Chelation: A Case of Three Aryldithiophosphinates
- Author
-
Lei Xu, Ping Yang, Jing Chen, Ning Pu, Jenifer C. Shafer, Chao Xu, Enrique R. Batista, Taoxiang Sun, and Jing Su
- Subjects
Lanthanide ,Trifluoromethyl ,010405 organic chemistry ,Ligand ,Chemistry ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,Group (periodic table) ,Electronic effect ,Chelation ,Desolvation ,Physical and Theoretical Chemistry - Abstract
Bis[o-(trifluoromethyl)phenyl]dithiophosphinate is a sulfur-donating ligand capable of providing the largest reported trivalent lanthanide (Ln3+)–actinide (An3+) group separation factors. Literatur...
- Published
- 2019
28. Enthalpies of formation and phase stability relations of USi, U3Si5 and U3Si2
- Author
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Andrew T. Nelson, C. K. Chung, Ping Yang, Anna Shelyug, Joshua T. White, Xiaofeng Guo, Hongwu Xu, Hakim Boukhalfa, Enrique R. Batista, Gaoxue Wang, Tashiema L. Wilson, Artaches Migdisov, Robert Roback, and Alexandra Navrotsky
- Subjects
Nuclear and High Energy Physics ,Materials science ,Intermetallic ,Thermodynamics ,02 engineering and technology ,Calorimetry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Standard enthalpy of formation ,010305 fluids & plasmas ,Tetragonal crystal system ,Nuclear Energy and Engineering ,0103 physical sciences ,General Materials Science ,Density functional theory ,Chemical stability ,Binary system ,0210 nano-technology ,Phase diagram - Abstract
U–Si intermetallic compounds have drawn great attention due to their potential application as nuclear fuels. However, the thermodynamic properties and phase equilibria of this binary system from ambient to high temperature conditions are not fully understood. Via high temperature oxidative drop calorimetry and detailed characterization of the initial and final phases, we have experimentally determined the standard enthalpies of formation of USi and U3Si5.07 at 298 K to be −43.2 ± 6.2 and −43.8 ± 9.0 kJ/mol·atom, respectively. The energetics of the tetragonal USi (t-USi, space group I4/mmm) phase has also been calculated with Density Functional Theory (DFT) for the first time. Combining the obtained formation enthalpies with the heat capacities measured previously, we assessed the thermodynamic stability of t-USi relative to a phase assemblage of two other U–Si phases, U3Si5.07 and U3Si2, from ambient temperature to 1200 K. The tetragonal USi is thermodynamically more stable than U3Si5.07 + U3Si2, which supports previously published phase diagram (H. Okamoto and T. Massalski, 1990 [1]): specifically, at least one stable USi phase exists when the U content is 50 at.%. Further thermodynamic and phase equilibrium studies are needed for a more comprehensive understanding of the U–Si system across broader compositional and temperature ranges.
- Published
- 2019
29. [Am(C 5 Me 4 H) 3 ]: An Organometallic Americium Complex
- Author
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Conrad A. P. Goodwin, Jing Su, Thomas E. Albrecht‐Schmitt, Anastasia V. Blake, Enrique R. Batista, Scott R. Daly, Stefanie Dehnen, William J. Evans, Andrew J. Gaunt, Stosh A. Kozimor, Niels Lichtenberger, Brian L. Scott, and Ping Yang
- Subjects
General Medicine - Published
- 2019
30. [Am(C 5 Me 4 H) 3 ]: An Organometallic Americium Complex
- Author
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Scott R. Daly, Andrew J. Gaunt, Thomas E. Albrecht-Schmitt, William J. Evans, Enrique R. Batista, Stosh A. Kozimor, Brian L. Scott, Stefanie Dehnen, Jing Su, Niels Lichtenberger, Ping Yang, Conrad A. P. Goodwin, and Anastasia V. Blake
- Subjects
Materials science ,actinides ,organometallic complexes ,structure elucidation ,Near-infrared spectroscopy ,chemistry.chemical_element ,Americium ,General Chemistry ,Actinide ,cyclopentadienyl ligands ,Catalysis ,americium ,chemistry ,Yield (chemistry) ,Physical chemistry ,Density functional theory ,Wave function ,Spectroscopy - Abstract
We report the small-scale synthesis, isolated yield, single-crystal X-ray structure, 1H NMR solution spectroscopy /solid-state UV/Vis-nIR spectroscopy, and density functional theory (DFT)/ab initio wave function theory calculations on an Am3+ organometallic complex, [Am(C5Me4H)3] (1). This constitutes the first quantitative data on Am−C bonding in a molecular species.
- Published
- 2019
31. Linked Picolinamide Nickel Complexes as Redox Carriers for Nonaqueous Flow Batteries
- Author
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Ivan A. Popov, Enrique R. Batista, Sandip Maurya, Benjamin L. Davis, Terry Chu, Rangachary Mukundan, Brian L. Scott, Ping Yang, and Gabriel A. Andrade
- Subjects
General Chemical Engineering ,Flow (psychology) ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Redox ,0104 chemical sciences ,Nickel ,General Energy ,chemistry ,Negative charge ,Environmental Chemistry ,Moiety ,lipids (amino acids, peptides, and proteins) ,General Materials Science ,0210 nano-technology - Abstract
The use of nickel complexes utilizing non-innocent ligands based on picolinamide to function as redox carriers in flow batteries was explored. The picolinamide moiety was linked together with -CH2 CH2 - (bpen), -CH2 CH2 CH2 - (bppn), and -C6 H4 - (bpb) moieties, resulting in two, three, and four quasi-reversible waves, respectively, for the nickel complexes and >3 V difference between the outermost positive and negative waves. The redox events were theoretically modelled for each complex, showing excellent agreement (
- Published
- 2019
32. Soft-donor dipicolinamide derivatives for selective actinide(<scp>iii</scp>)/lanthanide(<scp>iii</scp>) separation: the role of S- vs. O-donor sites
- Author
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Teresa M. Eaton, Konstantinos E. Papathanasiou, Christopher J. Dares, Konstantinos Kavallieratos, David Dan, Jiwen Jian, Jing Su, Ping Yang, Ingrid Lehman-Andino, Thomas E. Albrecht-Schmitt, Enrique R. Batista, and John K. Gibson
- Subjects
chemistry.chemical_classification ,Lanthanide ,Ligand ,Complex formation ,Extraction (chemistry) ,Metals and Alloys ,General Chemistry ,Actinide ,Medicinal chemistry ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,Materials Chemistry ,Ceramics and Composites ,Selectivity ,Thioamide - Abstract
Selectivity for An(iii) vs. Ln(iii) binding and extraction using dipicolinamide analogs containing the C[double bond, length as m-dash]O vs. C[double bond, length as m-dash]S groups was investigated in solution and the gas-phase, and by DFT calculations. The results show higher selectivity for complex formation and extraction for Am(iii) vs. Eu(iii) for the softer dithioamide vs. the diamide ligand, while in CH3CN the diamide binds more strongly than the thioamide to several Ln(iii), forming 1 : 1 complexes.
- Published
- 2019
33. Halide anion discrimination by a tripodal hydroxylamine ligand in gas and condensed phases
- Author
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Thibault Cheisson, Jiwen Jian, Michael R. Gau, Jing Su, Patrick J. Carroll, John K. Gibson, Enrique R. Batista, Eric J. Schelter, Teresa M. Eaton, and Ping Yang
- Subjects
Chemical Physics ,Collision-induced dissociation ,Ligand ,Electrospray ionization ,General Physics and Astronomy ,Halide ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Hydrogen halide ,chemistry.chemical_compound ,Engineering ,Hydroxylamine ,chemistry ,Physical Sciences ,Chemical Sciences ,Molecule ,Density functional theory ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
Electrospray ionization of solutions containing a tripodal hydroxylamine ligand, H3TriNOx ([((2-tBuNOH)C6H4CH2)3N]) denoted as L, and a hydrogen halide HX: HCl, HBr and/or HI, yielded gas-phase anion complexes [L(X)]- and [L(HX2)]-. Collision induced dissociation (CID) of mixed-halide complexes, [L(HXaXb)]-, indicated highest affinity for I- and lowest for Cl-. Structures and energetics computed by density functional theory are in accord with the CID results, and indicate that the gas-phase binding preference is a manifestation of differing stabilities of the HX molecules. A high halide affinity of [L(H)]+ in solution was also demonstrated, though with a highest preference for Cl- and lowest for I-, the opposite observation of, but not in conflict with, what is observed in gas phase. The results suggest a connection between gas- and condensed-phase chemistry and computational approaches, and shed light on the aggregation and anion recognition properties of hydroxylamine receptors.
- Published
- 2019
34. Solubility model of metal complex in ionic liquids from first principle calculations
- Author
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Enrique R. Batista, Anwesa Karmakar, Rangachary Mukundan, and Ping Yang
- Subjects
Chemistry ,General Chemical Engineering ,Solvation ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Ion ,Solvent ,Metal ,chemistry.chemical_compound ,visual_art ,Ionic liquid ,visual_art.visual_art_medium ,Molecule ,Physical chemistry ,Solubility ,0210 nano-technology ,Acetonitrile - Abstract
A predictive model based on first principles calculations has been proposed to study the solid–liquid equilibria comprising of metal complexes and ionic liquids. The model is based on first principle COSMO calculation followed by post statistical thermodynamical treatment of self-consistent properties of solute and solvent molecules. The metal complex and ionic liquid have been treated as a simple binary mixture. The ionic liquid has been treated here as a single intact molecule. The experimentally observed dual-solute relationship between the ionic liquid and redox active species in presence of a third organic solvent has been established using our model in this work. Within the model, the dual-solute relationship appeared as a simple Gibbs–Duhem relationship between these two species at ambient condition. The dual-solute relationship between the metal complex (V(acac)3, Cr(acac)3 and Mn(acac)3) and ionic liquid ([Tea][BF4]) has been validated by calculating the Gibbs–Duhem relationship, xsolute vs. xsolvent(IL) and 1/γsolute vs. xsolvent(IL) plots. The present model has been applied to a set of ionic liquids, metal complexes and organic solvent (acetonitrile) for which experimental study has been done. The solvation mechanism of the metal complexes in those ionic liquids was obtained using the model. According to our findings, the ionic liquid containing imidazolium cation and [NTf2]− anion is appeared as a suitable solvent for the non-aqueous redox flow cell. We have compared our results with the already reported experimental results where they were available for the non-aqueous solvents.
- Published
- 2019
35. Impact of Ligand Substitutions on Multielectron Redox Properties of Fe Complexes Supported by Nitrogenous Chelates
- Author
-
Enrique R. Batista, Ivan A. Popov, Benjamin L. Davis, Ping Yang, Nada Mehio, Rangachary Mukundan, and Terry Chu
- Subjects
High energy ,010405 organic chemistry ,Ligand ,Chemistry ,General Chemical Engineering ,Design elements and principles ,General Chemistry ,Electrolyte ,010402 general chemistry ,01 natural sciences ,Combinatorial chemistry ,Redox ,Article ,0104 chemical sciences ,lcsh:Chemistry ,Solvent ,lcsh:QD1-999 ,Chelation ,Electrochemical window - Abstract
Redox flow batteries (RFBs) have recently been recognized as a potentially viable technology for scalable energy storage. To take full advantage of RFBs, one possible approach for achieving high energy densities is to maximize a number of redox events by utilizing charge carriers capable of multiple one-electron transfers within the electrochemical window of solvent. However, past efforts to develop more efficient electrolytes for nonaqueous RFBs have mostly been empirical. In this manuscript, we shed light on design principles by theoretically investigating the effects of systematically substituting pyridyl moieties with imine ligands within a series of Fe complexes with some experimental validation. We found that such replacement is an effective strategy for reducing the molecular weight-to-charge ratios of these complexes. Simultaneously, calculations suggest that the reduction potentials and ligand-based redox activity of such substituted N-heterocyclic Fe compounds might be maintained within their +4 → -1 charge states. Additionally, by theoretically examining the role of coordination geometry, vis-à-vis reducing the number of redox noninnocent ligands within the first coordination sphere, we have demonstrated that Fe complexes with one such ligand were also capable of supporting multielectron reduction events and exhibited reduction potentials similar to their parent analogs supported by two or three of the same multidentate ligands. However, some differences in redox nature within the lower (+2 → -1) charge states were also noticed. Specifically, complexes containing two bidentate ligands, or one tridentate ligand, exhibited ligand-based reductions, whereas compounds with one bidentate ligand exhibited metal-centered reductions. The current results pave the way toward the design of the next-generation of Fe complexes with lower molecular weights and greater stored energy for redox flow batteries.
- Published
- 2018
36. A Comparative Review of Metal-Based Charge Carriers in Nonaqueous Flow Batteries
- Author
-
Tristan Pitt, Andrew Beamer, Harry D. Pratt, Benjamin L. Davis, Claudina X. Cammack, Enrique R. Batista, Travis M. Anderson, Travis C. Palmer, Ping Yang, and Ivan A. Popov
- Subjects
2019-20 coronavirus outbreak ,Service (systems architecture) ,Computer science ,business.industry ,General Chemical Engineering ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Grid ,01 natural sciences ,Energy storage ,0104 chemical sciences ,Renewable energy ,General Energy ,Flow (mathematics) ,Environmental Chemistry ,General Materials Science ,Charge carrier ,0210 nano-technology ,Process engineering ,business ,Voltage - Abstract
Energy storage is becoming the chief barrier to the utilization of more renewable energy sources on the grid. With independent service operators aiming to acquire gigawatts in the next 10-20 years, there is a large need to develop a suite of new storage technologies. Redox flow batteries (RFB) may be part of the solution if certain key barriers are overcome. Herein we focus on a particular kind of RFB based on nonaqueous media that promises to meet the challenge thru higher voltages than the organic and aqueous variants. This class of RFB will be divided into three groups, molecular, macromolecular, and redox-targeted based systems. The growing field of theoretical modeling will also be reviewed and discussed.
- Published
- 2021
37. SCC-DFTB Parameters for Fe-C Interactions
- Author
-
Marc J. Cawkwell, Elena Jakubikova, Néstor F. Aguirre, Enrique R. Batista, Chang Liu, and Ping Yang
- Subjects
Set (abstract data type) ,Chemistry ,Transferability ,Thermodynamics ,Physical and Theoretical Chemistry - Abstract
We present an optimized density-functional tight-binding (DFTB) parameterization for iron-based complexes based on the popular trans3d set of parameters. The transferability of the original and opt...
- Published
- 2020
38. Analysis of the thermodynamic stability of ThO2 and UO2 surfaces in the presence of surfactant ligands
- Author
-
Gaoxue Wang, David Gustavo Gonzalez, Enrique R. Batista, and Ping Yang
- Subjects
Pulmonary surfactant ,Chemistry ,Physical chemistry ,Chemical stability - Published
- 2020
39. Computational screening of two-dimensional coatings for semiconducting photocathodes
- Author
-
Ping Yang, Gaoxue Wang, and Enrique R. Batista
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,Graphene ,business.industry ,Nitride ,engineering.material ,law.invention ,chemistry.chemical_compound ,chemistry ,Coating ,law ,engineering ,Graphane ,Optoelectronics ,General Materials Science ,Quantum efficiency ,Work function ,MXenes ,business ,Visible spectrum - Abstract
Alkali-based semiconducting photocathodes, due to their high quantum efficiency (QE) in the visible light spectrum, are promising candidates to replace traditional metal photocathodes for high-brightness beam applications such as x-ray free electron lasers (XFELs). However, they suffer from rapid degradation which significantly limits their operational lifetimes. Coating them with two-dimensional (2D) materials has been proposed as a possible avenue to prevent the degradation. Ideally, the 2D coating layer should not increase the work function of semiconducting photocathodes, thus maintaining the high QE of semiconducting photocathodes in visible light. Herein, we report a computational screening of over 4000 2D materials in the Computational 2D Materials Database (C2DB). The assessment of their potential to be good coating layers is based on their effects to the surface electronic properties. We discover several candidate materials that are even capable of decreasing the work function of semiconducting photocathodes. Some of the experimentally synthesized 2D materials, such as hydrogenated graphene (graphane) and several hydroxylated transition metal carbides/nitrides (MXenes), are particularly appealing for this application.
- Published
- 2020
40. Development of Density Functional Tight-Binding Parameters Using Relative Energy Fitting and Particle Swarm Optimization
- Author
-
Amanda Morgenstern, Enrique R. Batista, Néstor F. Aguirre, Marc J. Cawkwell, and Ping Yang
- Subjects
Materials science ,010304 chemical physics ,Hydrogen ,chemistry.chemical_element ,Particle swarm optimization ,01 natural sciences ,Computer Science Applications ,Organic molecules ,Tight binding ,chemistry ,Chemical physics ,0103 physical sciences ,Development (differential geometry) ,Physical and Theoretical Chemistry ,Carbon ,Relative energy - Abstract
We provide a strategy to optimize density functional tight-binding (DFTB) parameterization for the calculation of the structures and properties of organic molecules consisting of hydrogen, carbon, nitrogen, and oxygen. We utilize an objective function based on similarity measurements and the Particle Swarm Optimization (PSO) method to find an optimal set of parameters. This objective function considers not only the common DFTB descriptors of binding energies and atomic forces but also incorporates relative energies of isomers into the fitting procedure for more chemistry-driven results. The quality in the description of the binding energies and atomic forces is measured based on the Ballester similarity index and relative energies through a similarity index induced by the Levenshtein edit distance to quantify the correct energetic order of isomers. Training and testing datasets were created to include all relevant chemical functional groups. The accuracy of this strategy is assessed, and its range of applicability is discussed by comparison against our previous parameterization [A. Krishnapriyan, et al.
- Published
- 2020
41. The duality of electron localization and covalency in lanthanide and actinide metallocenes
- Author
-
Richard L. Martin, Corwin H. Booth, Stefan G. Minasian, Jason M. Keith, David K. Shuh, David Clark, Tolek Tyliszczak, Enrique R. Batista, S. Chantal E. Stieber, Stosh A. Kozimor, and Danil E. Smiles
- Subjects
Delocalized electron ,Crystallography ,Chemistry ,Materials science ,Atomic orbital ,Chemical Sciences ,Density functional theory ,Strongly correlated material ,General Chemistry ,Time-dependent density functional theory ,Configuration interaction ,Ground state ,Electron localization function - Abstract
Previous magnetic, spectroscopic, and theoretical studies of cerocene, Ce(C8H8)2, have provided evidence for non-negligible 4f-electron density on Ce and implied that charge transfer from the ligands occurs as a result of covalent bonding. Strong correlations of the localized 4f-electrons to the delocalized ligand π-system result in emergence of Kondo-like behavior and other quantum chemical phenomena that are rarely observed in molecular systems. In this study, Ce(C8H8)2 is analyzed experimentally using carbon K-edge and cerium M5,4-edge X-ray absorption spectroscopies (XAS), and computationally using configuration interaction (CI) calculations and density functional theory (DFT) as well as time-dependent DFT (TDDFT). Both spectroscopic approaches provide strong evidence for ligand → metal electron transfer as a result of Ce 4f and 5d mixing with the occupied C 2p orbitals of the C8H82− ligands. Specifically, the Ce M5,4-edge XAS and CI calculations show that the contribution of the 4f1, or Ce3+, configuration to the ground state of Ce(C8H8)2 is similar to strongly correlated materials such as CeRh3 and significantly larger than observed for other formally Ce4+ compounds including CeO2 and CeCl62−. Pre-edge features in the experimental and TDDFT-simulated C K-edge XAS provide unequivocal evidence for C 2p and Ce 4f covalent orbital mixing in the δ-antibonding orbitals of e2u symmetry, which are the unoccupied counterparts to the occupied, ligand-based δ-bonding e2u orbitals. The C K-edge peak intensities, which can be compared directly to the C 2p and Ce 4f orbital mixing coefficients determined by DFT, show that covalency in Ce(C8H8)2 is comparable in magnitude to values reported previously for U(C8H8)2. An intuitive model is presented to show how similar covalent contributions to the ground state can have different impacts on the overall stability of f-element metallocenes., Unequivocal experimental evidence for carbon 2p and cerium 4f orbital mixing in cerocene, Ce(C8H8)2 is provided from carbon K-edge and Ce M5,4-edge X-ray absorption spectroscopies and corroborated with DFT and configuration interaction calculations.
- Published
- 2020
42. Advancing Chelation Chemistry for Actinium and Other +3 f-Elements, Am, Cm, and La
- Author
-
Eva R. Birnbaum, Stosh A. Kozimor, Brian L. Scott, Veronika Mocko, Samantha K. Cary, Ping Yang, Kevin D. John, Amanda Morgenstern, Benjamin W. Stein, Maryline G. Ferrier, Enrique R. Batista, Sharon E. Bone, and Juan S. Lezama Pacheco
- Subjects
Actinium ,Inorganic chemistry ,Binding pocket ,chemistry.chemical_element ,010402 general chemistry ,Ligands ,01 natural sciences ,Biochemistry ,Catalysis ,Coordination complex ,Colloid and Surface Chemistry ,Organophosphorus Compounds ,Coordination Complexes ,Lanthanum ,Molecule ,Chelation ,Chelating Agents ,chemistry.chemical_classification ,Americium ,Extended X-ray absorption fine structure ,Molecular Structure ,Extramural ,General Chemistry ,0104 chemical sciences ,chemistry ,Curium ,Radiopharmaceuticals - Abstract
A major chemical challenge facing implementation of 225Ac in targeted alpha therapy-an emerging technology that has potential for treatment of disease-is identifying an 225Ac chelator that is compatible with in vivo applications. It is unclear how to tailor a chelator for Ac binding because Ac coordination chemistry is poorly defined. Most Ac chemistry is inferred from radiochemical experiments carried out on microscopic scales. Of the few Ac compounds that have been characterized spectroscopically, success has only been reported for simple inorganic ligands. Toward advancing understanding in Ac chelation chemistry, we have developed a method for characterizing Ac complexes that contain highly complex chelating agents using small quantities (μg) of 227Ac. We successfully characterized the chelation of Ac3+ by DOTP8- using EXAFS, NMR, and DFT techniques. To develop confidence and credibility in the Ac results, comparisons with +3 cations (Am, Cm, and La) that could be handled on the mg scale were carried out. We discovered that all M3+ cations (M = Ac, Am, Cm, La) were completely encapsulated within the binding pocket of the DOTP8- macrocycle. The computational results highlighted the stability of the M(DOTP)5- complexes.
- Published
- 2019
43. Identification of the Formal +2 Oxidation State of Neptunium: Synthesis and Structural Characterization of {NpII[C5H3(SiMe3)2]3}1–
- Author
-
Andrew J. Gaunt, David H. Woen, Stosh A. Kozimor, Michael T. Janicke, Brian L. Scott, William J. Evans, Cory J. Windorff, Jing Su, Enrique R. Batista, and Ping Yang
- Subjects
010405 organic chemistry ,Chemistry ,Neptunium ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Characterization (materials science) ,Ion ,Crystallography ,Colloid and Surface Chemistry ,Oxidation state ,Density functional theory ,Electron configuration ,Ground state - Abstract
We report a new formal oxidation state for neptunium in a crystallographically characterizable molecular complex, namely Np2+ in [K(crypt)][NpIICp″3] [crypt = 2.2.2-cryptand, Cp″ = C5H3(SiMe3)2]. Density functional theory calculations indicate that the ground state electronic configuration of the Np2+ ion in the complex is 5f46d1.
- Published
- 2018
44. Overcoming the quantum efficiency-lifetime tradeoff of photocathodes by coating with atomically thin two-dimensional nanomaterials
- Author
-
Ping Yang, Enrique R. Batista, Gaoxue Wang, and Nathan A. Moody
- Subjects
02 engineering and technology ,engineering.material ,010402 general chemistry ,01 natural sciences ,Photocathode ,Nanomaterials ,law.invention ,lcsh:Chemistry ,Coating ,law ,Monolayer ,lcsh:TA401-492 ,General Materials Science ,Work function ,business.industry ,Graphene ,Mechanical Engineering ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Cathode ,0104 chemical sciences ,lcsh:QD1-999 ,Mechanics of Materials ,engineering ,Optoelectronics ,Quantum efficiency ,lcsh:Materials of engineering and construction. Mechanics of materials ,0210 nano-technology ,business - Abstract
Photocathodes are key components of electron injectors for X-ray free electron laser and X-ray energy recovery linacs, which generate brilliant, ultrafast, and coherent X-rays for the exploration of matter with ultrahigh resolutions in both space and time. Whereas alkali-based semiconducting photocathodes display a higher quantum efficiency (QE) in the visible light spectrum than their metallic counterparts, their lifetimes are much shorter due to the high reactivity of alkali-based surfaces to the residual gases in the vacuum chamber. Overcoming the tradeoff between QE and lifetimes has been a great challenge in the accelerator community. Herein, based on ab initio density functional calculations, we propose an approach to overcome this tradeoff by coating with atomically thin two-dimensional (2D) nanomaterials. On one hand, the 2D coating layers can enhance the lifetimes of photocathodes by preventing the chemical reactions with the residual gases. On the other hand, the 2D coating layers can effectively engineer the work function of photocathodes, thus controlling their QE. A monolayer of insulating BN reduces the work function, whereas a monolayer of semi-metallic graphene or semiconducting molybdenum disulfide (MoS2) increases the work function. This phenomenon originates from the induced interfacial dipoles. The reduction of work function by BN implies that it is capable of maintaining the high QE of semiconducting photocathodes in addition to enhance their lifetimes. This study advances our understandings on the surface chemistry of coated photocathodes and opens new technological avenues to fabricate photocathodes with high QE and longer lifetimes. Coating alkali-based photocathodes with atomically thin hBN enhance their lifetime whilst improving their quantum efficiency. A team led by Enrique Batista at Los Alamos National Laboratory performed ab initio density functional theory calculations on photocathodes coated with a variety of 2D materials. While monolayers of semi-metallic graphene and semiconducting MoS2 were found to increase the photocathode work function, a monolayer of insulating hBN led to a work function reduction whilst offering protection of the highly reactive photocathode surface from irreversible chemical reactions. Such work function reduction, key to achieving high quantum efficiency, was ascribed to the formation of induced dipole moments at the interface between hBN and the Cs3Sb cathode surface, pointing out of Cs3Sb. hBN monolayers are thus promising coating materials for alkali-based semiconducting photocathodes.
- Published
- 2018
45. Influence of Substituents on the Electronic Structure of Mono- and Bis(phosphido) Thorium(IV) Complexes
- Author
-
Pokpong Rungthanaphatsophon, Jochen Autschbach, Charles L. Barnes, Justin R. Walensky, Enrique R. Batista, Sean P. Vilanova, Thomas J. Duignan, Alexander J. Myers, and Ping Yang
- Subjects
Trimethylsilyl ,Absorption spectroscopy ,010405 organic chemistry ,Substituent ,Thorium ,chemistry.chemical_element ,Electronic structure ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Density functional theory ,Physical and Theoretical Chemistry ,Metallocene - Abstract
A series of metallocene thorium complexes with mono- and bis(phosphido) ligands have been investigated with varying hues: (C5Me5)2Th(Cl)[P(Mes)2] (Mes = mesityl = 2,4,6-(CH3)3C6H2; dark red-purple), (C5Me5)2Th[P(Mes)(CH3)]2 (dark red-purple), (C5Me5)2Th(CH3)[P(Mes)2] (dark red-purple), (C5Me5)2Th(CH3)[P(Mes)(SiMe3)] (orange), (C5Me5)2Th(Cl)[P(Mes)(SiMe3)] (orange), (C5Me5)2Th[P(Mes)(SiMe3)]2 (orange), and (C5Me5)2Th[PH(Mes)]2 (pale yellow). While all of these complexes bear a mesityl group on phosphorus, the electronic structure observed differs depending on the other substituent (mesityl, methyl, trimethylsilyl, or hydrogen). This sparked an investigation of the electronic structure of these complexes using 31P NMR and electronic absorption spectroscopy in concert with time-dependent density functional theory calculations.
- Published
- 2018
46. Spectroscopic and Computational Characterization of Diethylenetriaminepentaacetic Acid/Transplutonium Chelates: Evidencing Heterogeneity in the Heavy Actinide(III) Series
- Author
-
Corwin H. Booth, Rebecca J. Abergel, Morgan P. Kelley, Enrique R. Batista, Jing Su, Gauthier J.-P. Deblonde, and Ping Yang
- Subjects
Lanthanide ,Aqueous solution ,Extended X-ray absorption fine structure ,010405 organic chemistry ,chemistry.chemical_element ,General Chemistry ,Actinide ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Bond length ,Berkelium ,chemistry ,Molecule ,Physical chemistry ,Density functional theory - Abstract
The chemistry of trivalent transplutonium ions (Am3+ , Cm3+ , Bk3+ , Cf3+ , Es3+ …) is usually perceived as monotonic and paralleling that of the trivalent lanthanide series. Herein, we present the first extended X-ray absorption fine structure (EXAFS) study performed on a series of aqueous heavy actinide chelates, extending past Cm. The results obtained on diethylenetriaminepentaacetic acid (DTPA) complexes of trivalent Am, Cm, Bk, and Cf show a break to much shorter metal-oxygen nearest-neighbor bond lengths in the case of Cf3+ . Corroborating those results, density functional theory calculations, extended to Es3+ , suggest that the shorter Cf-O and Es-O bonds could arise from the departure of the coordinated water molecule and contraction of the ligand around the metal relative to the other [MIII DTPA(H2 O)]2- (M=Am, Cm, Bk) complexes. Taken together, these experimental and theoretical results demonstrate inhomogeneity within the trivalent transplutonium series that has been insinuated and debated in recent years, and that may also be leveraged for future nuclear waste reprocessing technologies.
- Published
- 2018
47. A series of dithiocarbamates for americium, curium, and californium
- Author
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Brian L. Scott, Shane S. Galley, Samantha K. Cary, Ping Yang, Cayla E. Van Alstine, Stosh A. Kozimor, Frankie D. White, Veronika Mocko, Thomas E. Albrecht-Schmitt, Jing Su, Maryline G. Ferrier, and Enrique R. Batista
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Lanthanide ,Materials science ,Series (mathematics) ,Curium ,010405 organic chemistry ,Analytical chemistry ,chemistry.chemical_element ,Californium ,Americium ,Actinide ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,chemistry - Abstract
Characterizing how actinide properties change across the f-element series is critical for improving predictive capabilities and solving many nuclear problems facing our society. Unfortunately, it is difficult to make direct comparisons across the 5f-element series because so little is known about trans-plutonium elements. Results described herein help to address this issue through isolation of An(S2CNEt2)3(N2C12H8) (Am, Cm, and Cf). These findings included the first single crystal X-ray diffraction measurements of Cm-S (mean of 2.86 ± 0.04 Å) and Cf-S (mean of 2.84 ± 0.04 Å) bond distances. Furthermore, they highlight the potential of An(S2CNEt2)3(N2C12H8) for providing a test bed for comparative analyses of actinide versus lanthanide bonding interactions.
- Published
- 2018
48. Revisiting complexation thermodynamics of transplutonium elements up to einsteinium
- Author
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Enrique R. Batista, Ping Yang, Sergey I. Sinkov, Jenifer C. Shafer, Jing Su, Morgan P. Kelley, Nathan P. Bessen, Matthew Urban, and Gregg J. Lumetta
- Subjects
010405 organic chemistry ,Chemistry ,Metals and Alloys ,chemistry.chemical_element ,General Chemistry ,Actinide ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Computational chemistry ,Einsteinium ,Materials Chemistry ,Ceramics and Composites - Abstract
Literature casts einsteinium as a departure from earlier transplutonium actinides, with a decrease in stability constants with aminopolycarboxylate ligands. This report studies transplutonium chemistry - including Am, Bk, Cf, and Es - with aminopolycarboxylate ligands. Es complexation follows similar thermodynamic and structural trends established by the earlier actinides, consistent with first-principle calculations.
- Published
- 2018
49. Quantitative Evidence for Lanthanide-Oxygen Orbital Mixing in CeO2, PrO2, and TbO2
- Author
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Enrique R. Batista, S. Chantal E. Stieber, David Clark, Richard L. Martin, Stefan G. Minasian, Stosh A. Kozimor, Jason M. Keith, David K. Shuh, Xiaodong Wen, Wayne W. Lukens, Corwin H. Booth, and Tolek Tylisczcak
- Subjects
Lanthanide ,X-ray absorption spectroscopy ,Absorption spectroscopy ,Chemistry ,Ionic bonding ,02 engineering and technology ,General Chemistry ,Electronic structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Colloid and Surface Chemistry ,Atomic orbital ,Covalent bond ,Physical chemistry ,Density functional theory ,0210 nano-technology - Abstract
© 2017 American Chemical Society. Understanding the nature of covalent (band-like) vs ionic (atomic-like) electrons in metal oxides continues to be at the forefront of research in the physical sciences. In particular, the development of a coherent and quantitative model of bonding and electronic structure for the lanthanide dioxides, LnO2(Ln = Ce, Pr, and Tb), has remained a considerable challenge for both experiment and theory. Herein, relative changes in mixing between the O 2p orbitals and the Ln 4f and 5d orbitals in LnO2are evaluated quantitatively using O K-edge X-ray absorption spectroscopy (XAS) obtained with a scanning transmission X-ray microscope and density functional theory (DFT) calculations. For each LnO2, the results reveal significant amounts of Ln 5d and O 2p mixing in the orbitals of t2g(σ-bonding) and eg(π-bonding) symmetry. The remarkable agreement between experiment and theory also shows that significant mixing with the O 2p orbitals occurs in a band derived from the 4f orbitals of a2usymmetry (σ-bonding) for each compound. However, a large increase in orbital mixing is observed for PrO2that is ascribed to a unique interaction derived from the 4f orbitals of t1usymmetry (σ- and π-bonding). O K-edge XAS and DFT results are compared with complementary L3-edge and M5,4-edge XAS measurements and configuration interaction calculations, which shows that each spectroscopic approach provides evidence for ground state O 2p and Ln 4f orbital mixing despite inducing very different core-hole potentials in the final state.
- Published
- 2017
50. Covalency in Americium(III) Hexachloride
- Author
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Stosh A. Kozimor, Justin N. Cross, Brian L. Scott, Samantha K. Cary, Ping Yang, Enrique R. Batista, Cory J. Windorff, Benjamin W. Stein, William J. Evans, Jing Su, and Veronika Mocko
- Subjects
X-ray absorption spectroscopy ,Americium ,Absorption spectroscopy ,010405 organic chemistry ,Chemistry ,Extramural ,chemistry.chemical_element ,General Chemistry ,Electronic structure ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Colloid and Surface Chemistry ,Chlorides ,Chemical physics ,Computational chemistry ,Mixing (physics) - Abstract
Developing a better understanding of covalency (or orbital mixing) is of fundamental importance. Covalency occupies a central role in directing chemical and physical properties for almost any given compound or material. Hence, the concept of covalency has potential to generate broad and substantial scientific advances, ranging from biological applications to condensed matter physics. Given the importance of orbital mixing combined with the difficultly in measuring covalency, estimating or inferring covalency often leads to fiery debate. Consider the 60-year controversy sparked by Seaborg and co-workers ( Diamond, R. M.; Street, K., Jr.; Seaborg, G. T. J. Am. Chem. Soc. 1954 , 76 , 1461 ) when it was proposed that covalency from 5f-orbitals contributed to the unique behavior of americium in chloride matrixes. Herein, we describe the use of ligand K-edge X-ray absorption spectroscopy (XAS) and electronic structure calculations to quantify the extent of covalent bonding in-arguably-one of the most difficult systems to study, the Am-Cl interaction within AmCl
- Published
- 2017
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