Article
Chemistry, Multidisciplinary
Laure Decamps, Derek B. Rice, Serena DeBeer
Summary: This study provides experimental evidence that the cofactor of the iron nitrogenase contains a carbide, making the Fe6C core a common feature among all nitrogenase cofactors.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Multidisciplinary
Rebeca G. Castillo, Anselm W. Hahn, Benjamin E. Van Kuiken, Justin T. Henthorn, Jeremy McGale, Serena DeBeer
Summary: Resonant X-ray emission spectroscopy (XES) is demonstrated to be able to recover physical oxidation state information in highly covalent systems, providing a straightforward way to resolve previously ambiguous oxidation state assignments. This approach offers chemists a more rigorous and quantitative method to address challenging electronic-structure questions.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Astronomy & Astrophysics
Ang Li, Zhiqiang Miao, Sophia Han, Bing Zhang
Summary: In this study, a Bayesian analysis was conducted on the maximum mass of neutron stars with a quark core, revealing the most probable values of the hybrid star maximum mass to be around 2.36 solar masses. The results are robust with respect to uncertainties in the hadronic EOS and have implications for astrophysical phenomena such as post-merger products of neutron star mergers and short gamma-ray bursts.
ASTROPHYSICAL JOURNAL
(2021)
Review
Chemistry, Physical
George E. Cutsail, Serena DeBeer
Summary: X-ray spectroscopy plays a significant role in catalysis research by providing essential electronic and geometric structural information. The development of dedicated synchrotron-based X-ray emission spectrometers has expanded experimental capabilities, offering more detailed data. There is a continuous demand for conventional XAS applications and the integration with more advanced techniques.
Article
Chemistry, Physical
T. J. Penfold, C. D. Rankine
Summary: In this article, we extend a deep neural network to predict the lineshape of first-row transition metal spectra. We demonstrate that the network can reproduce main spectral features using only local coordination geometry as input. We also explore three methods for assessing uncertainty in the predictions and find that bootstrap resampling performs best.
Article
Multidisciplinary Sciences
J. Niskanen, A. Vladyka, J. Niemi, C. J. Sahle
Summary: In this study, we explore the sensitivity of several core-level spectroscopic methods to the atomistic structure using water molecule as a test system. We define a metric to measure the magnitude of spectral change as a function of structure, which enables us to identify structural regions with high spectral sensitivity. By employing machine-learning emulator-based decomposition of structural parameter space, we are able to recover more spectral variance and identify spectroscopically dominant degrees of freedom.
ROYAL SOCIETY OPEN SCIENCE
(2022)
Article
Nanoscience & Nanotechnology
Hassan Javed, Axel Knop-Gericke, Rik V. Mom
Summary: Potential spikes during start-up and shutdown of fuel cells cause platinum electrocatalyst degradation. In this study, XPS is used to investigate the oxidation states of platinum during fuel cell operation and it is found that a mixed surface oxide is formed at high potentials. The description of platinum oxidation is valid during transient conditions of fuel cell start-up and shutdown.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Chemistry, Physical
Anita Bagri, Sophia Sahoo, R. J. Choudhary, D. M. Phase
Summary: The study investigates the electronic, magnetic, and transport properties of an oxygen-deficient epitaxial SrRuO3 thin film, where oxygen vacancies transform Ru4+ ions into Ru3+ leading to an enhanced unit cell volume. The elongated lattice parameters result in decreased electronic bandwidth and enhanced correlation strength, with distinctive effects observed in the temperature-dependent resistivity behavior. Furthermore, the low-temperature resistivity upturn behavior of the oxygen-deficient SrRuO3 thin film is found to be dominated by weak localization over renormalized electron-electron interactions.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Environmental Sciences
Gonzalo Bia, M. Gabriela Garcia, Nicolas J. Cosentino, Laura Borgnino
Summary: This study investigates the abundance, speciation, and dispersion of arsenic (As) in fresh volcanic ash from explosive Patagonian eruptions. Results show that the concentration, speciation, and mobility of As depend on the silica content of source magmas. Arsenic mainly accumulates on the surface of Al-silicate glass in volcanic ash. Atmospheric dispersion simulations reveal the impact of As-bearing ash on groundwater in Patagonia and surrounding areas.
SCIENCE OF THE TOTAL ENVIRONMENT
(2022)
Article
Chemistry, Physical
Viktoriia A. Saveleva, Kavita Kumar, Pascal Theis, Nicole Segura Salas, Ulrike I. Kramm, Frederic Jaouen, Frederic Maillard, Pieter Glatzel
Summary: This study investigates the structural composition of Fe-N-C materials for the oxygen reduction reaction in proton-exchange membrane fuel cells, before and after catalyst layer preparation, using X-ray absorption and emission spectroscopies. The results reveal the significant impact of the preparation step on the electronic structure and local coordination of Fe, emphasizing the importance of determining the Fe-N-C catalyst structure in the prepared electrode for further studies of the structure-activity-stability correlations.
ACS APPLIED ENERGY MATERIALS
(2023)
Article
Chemistry, Physical
Diana M. Arciniegas Jaimes, Valeria C. Fuertes, M. Cecilia Blanco, German Tirao, Silvina Limandri, Vivian M. Nassif, Gabriel J. Cuello, Alejandro Rodriguez, Edilso Reguera, Raul E. Carbonio
Summary: This study reports the synthesis, structural characterization, and magnetic properties of La3Mn2NbO9 double perovskite. The crystal structure shows a high degree of cation order and magnetization measurements reveal the presence of ferromagnetic and antiferromagnetic interactions at different temperatures.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Chemistry, Inorganic & Nuclear
Isabelle Gerz, Sergio Augusto Venturinelli Jannuzzi, Knut T. Hylland, Chiara Negri, David S. Wragg, Sigurd Oien-Odegaard, Mats Tilset, Unni Olsbye, Serena DeBeer, Mohamed Amedjkouh
Summary: A series of Cu(I) complexes with bidentate or tetradentate Schiff base ligands containing 1-H-imidazole or pyridine moieties were synthesized and studied using NMR and X-ray spectroscopic techniques. The nature of the heterocycle in the ligands strongly affected the coordination shifts of N-15(imine) in the complexes, which correlated well with the Cu-N-imine bond lengths from single-crystal X-ray diffraction measurements. Variable-temperature NMR experiments revealed a temperature-dependent interconversion in one complex, while Cu K-edge XAS and VtC XES studies suggested the formation of polynuclear oligomers in solid state for complexes with tetradentate imidazole ligands. Incorporation of a Cu(II) analogue into a MOF resulted in discrete, mononuclear complexes in the solid state.
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
(2021)
Article
Chemistry, Physical
Edgars Butanovs, Alexei Kuzmin, Sergei Piskunov, Krisjanis Smits, Aleksandr Kalinko, Boris Polyakov
Summary: The study demonstrates the growth of high-quality few-layer ReS2 using pre-deposited rhenium oxide coating on different semiconductor material nanowires, creating novel core-shell heterostructures for energy applications involving photocatalytic and electrocatalytic hydrogen evolution.
APPLIED SURFACE SCIENCE
(2021)
Article
Chemistry, Physical
Sven Struebbe, Michal Nowakowski, Roland Schoch, Matthias Bauer
Summary: A new approach is presented for characterizing CO2 methanation catalysts prepared by thermal decomposition of a nickel MOF. This approach uses high energy resolution fluorescence detected X-ray absorption near edge structure spectroscopy (HERFD-XANES) and valence-to-core X-ray emission (VtC-XES) techniques, which allow for a more precise phase determination of the catalyst influenced by the MOF decomposition conditions.
Review
Crystallography
Krystyna A. Deresz, Piotr Laski, Radoslaw Kaminski, Katarzyna N. Jarzembska
Summary: This review provides an overview of methods for tracing photoexcitation processes and structural dynamics in the solid state, with a focus on X-ray diffraction techniques. The recent developments and experimental possibilities in the field are discussed, along with data processing and analysis approaches, and illustrated with examples of successful studies. Additionally, selected complementary methods such as ultrafast electron diffraction or time-resolved X-ray absorption spectroscopy are briefly presented.
Article
Chemistry, Physical
Matyas Papai
Summary: A new theoretical approach combining electronic structure and spin-vibronic dynamics methods is applied to study the photoswitching dynamics of an octahedral model complex. The method accurately simulates the transition processes and locates the positions of the transitions. This efficient approach is important for the study of photoswitching materials and ultrafast experiments.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2022)
Article
Chemistry, Physical
Anna Kristina Schnack-Petersen, Matyas Papai, Klaus Braagaard Moller
Summary: The photoisomerization reaction of azobenzene in both directions was investigated using the surface hopping procedure with forced jumps based on density functional theory. It was found that the cis to-trans isomerization proceeds stepwise, while the trans-to-cis isomerization occurs in one smooth step. The analysis revealed that two coupled modes must be considered for a fuller picture of the cis to-trans isomerization, while the trans-to-cis isomerization can be well described along only the CNNC dihedral angle. The study provides insights into the interpretation of experimental observations and shows a heavy functional dependency in the structures of the conical intersections (CIs) for both reactive and non-reactive trajectories.
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY
(2022)
Article
Instruments & Instrumentation
Antal Mikehazi, Jihad El Guettioui, Istvan B. Foldes, Gyorgy Vanko, Zoltan Nemeth
Summary: The present work demonstrates the performance of a von Hamos high-energy-resolution X-ray spectrometer based on a non-conventional conical Si single-crystal analyzer. Both experimental and simulated results affirm the efficient detection and resolution ability of the conical spectrometer, making it suitable for various applications.
JOURNAL OF SYNCHROTRON RADIATION
(2022)
Article
Chemistry, Multidisciplinary
Tetsuo Katayama, Tae-Kyu Choi, Dmitry Khakhulin, Asmus Dohn, Christopher Milne, Gyoergy Vanko, Zoltan Nemeth, Frederico Lima, Jakub Szlachetko, Tokushi Sato, Shunsuke Nozawa, Shin-ichi Adachi, Makina Yabashi, Thomas Penfold, Wojciech Gawelda, Gianluca Levi
Summary: By simultaneously measuring femtosecond X-ray emission and scattering, the intramolecular and solvation structural dynamics following photoexcitation of a solvated copper photosensitizer were tracked. The results reveal that photoinduced solute and solvent motions can be intimately intertwined, explaining the influence of the solvent on the initial steps of light harvesting. This work is a step forward in understanding the microscopic mechanisms of the bidirectional influence between transient solvent reorganization and photoinduced solute structural dynamics.
Article
Chemistry, Multidisciplinary
Tamas Rozgonyi, Gyorgy Vanko, Matyas Papai
Summary: It is well known that visible light can convert Fe(II) polypyridines from low-spin state to high-spin state, but the mechanism is still controversial. In this study, we simulated the singlet-triplet-quintet dynamics of [Fe(terpy)(2)](2+) complex in order to clarify the photodynamics. We report a branching mechanism involving two sequential processes, and show that the quintet state is populated on a sub-picosecond timescale with non-exponential dynamics and coherent Fe-N breathing oscillations.
COMMUNICATIONS CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Ana F. Suzana, Sizhan Liu, Jiecheng Diao, Longlong Wu, Tadesse A. Assefa, Milinda Abeykoon, Ross Harder, Wonsuk Cha, Emil S. Bozin, Ian K. Robinson
Summary: When synthesized under certain conditions, barium titanate (BTO) nanoparticles show a non-thermodynamic cubic structure and have an enhanced dielectric constant. These nanoparticles are widely used in thin-layer capacitors. Characterization methods, including X-ray refinement and the Williamson-Hall approach, reveal the presence of notable strain associated with the cubic phase. However, X-ray pair distribution function measurements indicate a lower symmetry local structure.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Chemistry, Inorganic & Nuclear
Mariann Papp, Tamas Keszthelyi, Andor Vancza, Eva G. Bajnoczi, Eva Kovats, Zoltan Nemeth, Csilla Bogdan, Gabor Bazso, Tamas Rozgonyi, Gyorgy Vanko
Summary: In this paper, the effects of ligand substitutions on the electronic structure and properties of transition-metal complexes are investigated theoretically and experimentally. It is found that substitution with a Cl atom at different positions of the terpyridine ligand can effectively modify the electronic structure of the complexes and significantly impact the excited state lifetime. These findings contribute to the development of molecular engineering for similar complexes.
INORGANIC CHEMISTRY
(2023)
Article
Chemistry, Physical
Anna Kristina Schnack-Petersen, Matyas Papai, Sonia Coriani, Klaus Braagaard Moller
Summary: The time-resolved x-ray absorption spectrum of BT-1T cation (BT-1T(+)) is simulated using trajectory surface hopping and quantum dynamics to investigate the charge transfer reaction. Static x-ray absorption spectra (XAS) of ground and excited states are calculated using time-dependent density functional theory and coupled cluster singles and doubles method, yielding consistent results. Small structural changes during the reaction have little impact on static XAS, thus enabling tr-XAS calculation based on state populations from nuclear dynamics simulation and a single set of static XAS calculations. This approach, applicable for investigating non-radiative decay processes near the Franck-Condon point in rigid molecules like BT-1T, saves computational resources.
STRUCTURAL DYNAMICS-US
(2023)
Article
Instruments & Instrumentation
F. A. Lima, F. Otte, M. Vakili, F. Ardana-Lamas, M. Biednov, F. Dall'Antonia, P. Frankenberger, W. Gawelda, L. Gelisio, H. Han, X. Huang, Y. Jiang, M. Kloos, T. Kluyver, M. Knoll, K. Kubicek, I. J. Bermudez Macias, J. Schulz, O. Turkot, Y. Uemura, J. Valerio, H. Wang, H. Yousef, P. Zalden, D. Khakhulin, C. Bressler, C. Milne
Summary: The Femtosecond X-ray Experiments (FXE) instrument at the European X-ray Free-Electron Laser (EuXFEL) is optimized for studying ultrafast physical, chemical, and biological processes. It utilizes diverse ultrafast X-ray spectroscopic, scattering, and diffraction techniques and operates at a flexible energy range of 4.7-20 keV. The instrument is particularly suitable for experiments that take advantage of the sub-MHz repetition rates provided by the EuXFEL.
JOURNAL OF SYNCHROTRON RADIATION
(2023)
Article
Chemistry, Inorganic & Nuclear
Mariann Papp, Tamas Keszthelyi, Andor Vancza, Eva G. Bajnoczi, Eva Kovats, Zoltan Nemeth, Csilla Bogdan, Gabor Bazso, Tamas Rozgonyi, Gyorgy Vanko
Summary: The properties and dynamics of transition-metal complexes can be effectively modified with ligand substitutions, and theory plays a crucial role in molecular engineering. This study explores the electronic structure and ground state properties of Fe(II) complexes with terpyridine ligand substitutions. The results show that substitution at positions 5 and 5'' with Cl has a significant effect on the energy and lifetime of the quintet state.
INORGANIC CHEMISTRY
(2023)
Article
Chemistry, Physical
Matyas Papai, Tamas Rozgonyi, Gyoergy Vanko
Summary: The application of N-heterocyclic carbene (NHC) ligands in light-harvesting complexes has made significant progress, but there are still controversies regarding the excited-state dynamics of Fe-NHC photosensitizers. Using simulations, this study clarifies the deactivation mechanism of [Fe(bmip)2](2+) and finds that the photosensitizing efficiency is weakened by the ultrafast quenching of the triplet metal-to-ligand charge transfer by metal-centered states. Experimental data also suggest the presence of early sub-picosecond metal-centered states.
JOURNAL OF MATERIALS CHEMISTRY A
(2023)
Article
Materials Science, Multidisciplinary
Ericmoore Jossou, Tadesse A. Assefa, Ana F. Suzana, Longlong Wu, Colleen Campbell, Ross Harder, Wonsuk Cha, Kim Kisslinger, Cheng Sun, Jian Gan, Lynne Ecker, Ian K. Robinson, Simerjeet K. Gill
Summary: Radiation-induced materials degradation is a major concern in nuclear materials performance. The formation of nanoscale void and gas bubble superlattices can effectively mitigate radiation-induced damage and aid the development of radiation tolerant materials. This study used multi-reflection Bragg coherent diffraction imaging to quantify the strain induced by void superlattices in iron irradiated chromium substrate, providing a quantitative estimation of three-dimensional strain and predicting defect density with high sensitivity. This approach can significantly improve the understanding and prediction of materials behavior in radiation environments and revolutionize the design of radiation tolerant materials.
NPJ MATERIALS DEGRADATION
(2022)
Article
Chemistry, Physical
Habiburrahman Zulfikri, Matyas Papai, Asmus Ougaard Dohn
Summary: When characterizing transition metal complexes and their functionalities, the importance of including the solvent as an active participant is becoming more apparent. The study reveals that long-range dispersion effects modulate the coordination in solvation and can be accurately captured by density functional theory models including dispersion corrections.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
