Article
Physics, Applied
T. R. Rajalekshmi, Vikash Mishra, Tejendra Dixit, Pankaj R. Sagdeo, M. S. Ramachandra Rao, K. Sethupathi
Summary: In this study, the origin of three energy gaps in lanthanum chromium oxide is analyzed using diffuse reflectance spectroscopy. The results show charge-transfer and d-d transitions as the sources of the gaps. The use of Tanabe-Sugano diagram and absorption spectrum helps in understanding the spin allowed and parity forbidden transitions. The findings have significant implications in laser applications and the development of optoelectronic devices.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Multidisciplinary
Luke Thatcher, Parker Fairfield, Lazaro Merlo-Ramirez, Juan M. Merlo
Summary: This work reports the experimental observation of topological phase transition in a mechanical one-dimensional topological insulator using the Su-Schrieffer-Heeger (SSH) model. The mechanical system consisted of an elastic string with metallic masses emulating atomic sites, and the interaction strengths were controlled by the distances between the masses. The experimental observations were supported by numerical and theoretical models, and the work allows for the study of topological phase transitions in mechanical systems with materials available in any research lab.
Article
Materials Science, Ceramics
Sunil Kumar, Manoj Kumar, Srihari Velaga, Amarjeet Singh
Summary: The optical properties of a precursor dry Ferritin powder and its iron oxide derivatives were studied using UV-visible spectroscopy. The iron oxide derivatives exhibit significant changes in absorption spectra with annealing temperature, showing a large shift in absorption band edge. Crystallization and thermal destruction of the organic cage are found to be inter-related. The large absorption band edge shift provides a simple approach to tuneable optical properties of iron oxides.
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY
(2023)
Article
Physics, Multidisciplinary
Alexander Osterkorn, Constantin Meyer, Salvatore R. Manmana
Summary: This study reveals that in a driven strongly interacting system, a band-like resonance is formed in the gap region. This phenomenon is associated with the Villain mode and appears in both equilibrium and non-equilibrium states.
COMMUNICATIONS PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Ethan Chi Ho Wen, Peter H. Jacobse, Jingwei Jiang, Ziyi Wang, Steven G. Louie, Michael F. Crommie, Felix R. Fischer
Summary: Substitutional heteroatom doping in 1D graphene nanoribbons is a versatile tool for low-dimensional functional materials, but previous methods only result in modest realignment of energy levels. This study introduces nitrogen core-doped armchair GNRs that yield greater energy-level shifting through the substitution of carbon atoms with nitrogen atoms along the backbone.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Materials Science, Multidisciplinary
Yuan Yao, Akira Furusaki
Summary: We propose a geometric approach to the Lieb-Schultz-Mattis theorem for quantum many-body systems with discrete spin-rotation symmetries and lattice inversion or rotation symmetry, but without translation symmetry assumed. Under symmetry twisting, we find that doubly degenerate spectra exist in d-dimensional inversion-symmetric spin systems with half-integer spins at the inversion-symmetric point. We also observe a similar degeneracy in rotation-symmetric generalized spin models with projective representations at the rotation center. These degeneracies imply the absence of a unique symmetric gapped ground state connected to product states in the original untwisted systems without lattice translation symmetry imposed.
Article
Materials Science, Multidisciplinary
Maria Hellgren, Lucas Baguet, Matteo Calandra, Francesco Mauri, Ludger Wirtz
Summary: The study demonstrates the importance of including exact exchange for describing the electronic and vibrational properties of TiSe2. The developed quasi-self-consistent extension of G(0)W(0) based on the random phase approximation and hybrid density functional theory is crucial for systems like TiS2 and TiSe2, providing an optimal starting point and consistent hybrid exchange parameters. The high-temperature phase of TiSe2 is found to be a semimetal with a band structure in good agreement with experimental results, while the optimized hybrid functional accurately reproduces the low-temperature charge-density-wave phase.
Article
Materials Science, Multidisciplinary
Masato Fujii, Tomoyuki Yamaguchi, Takuo Ohkochi, Chandan De, Sang-Wook Cheong, Takashi Mizokawa
Summary: The bulk and surface electronic states of MnPSe3 were studied using X-ray photoemission spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and theoretical calculations. The results indicate that in Mn 2p XPS, the main peak is accompanied by a charge-transfer satellite, which is reduced by surface oxidization. The multiplet structure of Mn 2p XAS suggests a high spin Mn2+ configuration.
Article
Chemistry, Multidisciplinary
Amanpal Singh, Yogesh Kumar Saini, Anuj Kumar, Sanjeev Gautam, Dinesh Kumar, Viresh Dutta, Han-koo Lee, Jongsu Lee, Sanjay Kumar Swami
Summary: Graphene oxide (GO) nano-powder is synthesized using the modified Hummer's method and thin films are deposited using a GO water solution. The thermal reduction of GO allows for control of microstructural, electrical, and optical properties. The addition of reduced GO nano-powder to TiO2 paste significantly improves the performance of dye-sensitized solar cells (DSSCs) compared to unmodified TiO2 photoanodes.
Article
Physics, Applied
Xue Zhou, Jinye Tong, Jie Chang, Zhixia Xu
Summary: In this study, the change of topological edge waves by gliding the photonic crystals (PhCs) was investigated. The experiments and simulations showed that glide-symmetric dislocation is an essential degree of freedom to manipulate topological edge waves.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Hengxin Tan, Binghai Yan
Summary: Magnetic topological insulators (MnBi2Te4)(Bi2Te3)(n) (n = 0, 1, 2, 3) have the potential to achieve exotic topological states such as the quantum anomalous Hall effect (QAHE) and axion insulator (AI). However, the debate over whether the surface states on the Bi2Te3 layer are gapless or gapped, and their consequences in thin-film properties, is ongoing. In this study, calculations show that the Bi2Te3 terminated facets are gapless for compounds with n ≥ 1. This poses a challenge for realizing QAHE or AI, which require an insulating gap in thin films with at least one Bi2Te3 surface. The insulating phase can still be achieved in a film if both surfaces are MnBi2Te4 layers or if the film thickness is less than 10-20 nm, which can push down the bulk valence bands through the size effect.
Article
Chemistry, Physical
Xianshang Meng, Hanlu Liu, Like Lin, Yingbin Cheng, Xuan Hou, Siyang Zhao, Haiming Lu, Xiangkang Meng
Summary: The research found that various groups III-VIIA atoms can chemisorb with 2D GaN, introducing magnetic features and different electronic structures. Adsorption of different elements can modify the physical properties of 2D GaN, with potential applications in electronic, optoelectronic, and spintronic fields.
APPLIED SURFACE SCIENCE
(2021)
Article
Chemistry, Inorganic & Nuclear
R. Mojica, A. E. Torres, I. Zumeta-Dube, Y. Avila, E. Reguera
Summary: This study investigates the electronic structure of mercury nitroprusside and elucidates the nature of the electronic transitions that explain its optical response. Experimental and computational methods were employed to analyze the influence of mercury ion valence on the electronic structure.
JOURNAL OF SOLID STATE CHEMISTRY
(2022)
Article
Chemistry, Multidisciplinary
Peng Li, Jinjun Ding, Steven S-L Zhang, James Kally, Timothy Pillsbury, Olle G. Heinonen, Gaurab Rimal, Chong Bi, August DeMann, Stuart B. Field, Weigang Wang, Jinke Tang, Jidong Samuel Jiang, Axel Hoffmann, Nitin Samarth, Mingzhong Wu
Summary: This study reports a genuine topological Hall effect in a TI/MI structure, where the contribution of skyrmions to the Hall effect outweighs the coexistence of magnetic phases.
Article
Materials Science, Multidisciplinary
Xiaolan Du, Chao An, Xuliang Chen, Ying Zhou, Min Zhang, Shuyang Wang, Chunhua Chen, Yonghui Zhou, Xiaoping Yang, Zhaorong Yang
Summary: The structural and electronic properties of CaCdGe, a nodal-line semimetal candidate, were studied under pressure up to 53.3 GPa using synchrotron x-ray diffraction, Raman scattering, electrical transport measurements, and theoretical calculations. Although no clear structural transition was observed, abnormal changes in bond angles and a new Raman peak were found around a certain pressure point (PC). The resistance parameters also showed abrupt changes above PC, suggesting the occurrence of a subtle isostructural transition due to the distortion of CdGe4 tetrahedra.
Article
Chemistry, Physical
Giovanni Di Liberto, Luis A. Cipriano, Gianfranco Pacchioni
Summary: This article investigates the relationship between metal atoms and their surrounding environment in single atom catalysts (SACs). The numerical experiments reveal that changing the active site or the surrounding environment can lead to significant variations in catalytic activity. The implications of this conclusion for modeling studies of SACs are discussed.
Article
Chemistry, Physical
Giovanni Di Liberto, Farahnaz Maleki, Gianfranco Pacchioni
Summary: This study conducted ab initio molecular dynamics simulations using density functional theory to investigate the pH-dependent surface chemistry of MgO, TiO2, and γ-Al2O3, successfully predicting the point-of-zero charge values and the proportions of charged species and neutral molecules on the surface as pH varies.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Multidisciplinary Sciences
Ilaria Barlocco, Luis A. Cipriano, Giovanni Di Liberto, Gianfranco Pacchioni
Summary: This study investigates the impact of different exchange-correlation functionals on the catalytic activity of single atom catalysts in hydrogen and oxygen evolution reactions. The results show that the choice of functional can lead to significant deviations in the predicted activity for different transition metals.
ADVANCED THEORY AND SIMULATIONS
(2023)
Article
Chemistry, Physical
Giovanni Di Liberto, Sergio Tosoni
Summary: We investigated the interface between carbon nitride (C3N4) and phosphorene nanosheets (P-ene) using Density Functional Theory (DFT) calculations. The formation of the interface is driven by Van der Waals forces. The thickness of P-ene nanosheets determines the band edges offsets and the separation of charge carriers. The system transitions from a nearly type-II to a type-I junction as the thickness of P-ene increases.
Review
Chemistry, Physical
Sergio Tosoni, Giovanni Di Liberto, Ivana Matanovic, Gianfranco Pacchioni
Summary: In this tutorial review, the state-of-the-art modeling approaches of Single Atom Catalysts (SAC) for water splitting and fuel cells reactions are reported. The discussion focuses on Hydrogen Evolution Reaction (HER), Oxygen Reduction Reaction (OER), Hydrogen Oxidation Reaction (HOR), and Oxygen Reduction Reaction (ORR). The aim is to emphasize the relevant aspects of SACs modeling and provide guidance for computational chemists and experimentalists. The review covers methodologies, prediction of electronic properties, validation of structural models, prediction of catalytic activity and selectivity, and analysis of current challenges and limitations.
JOURNAL OF POWER SOURCES
(2023)
Article
Nanoscience & Nanotechnology
Farahnaz Maleki, Giovanni Di Liberto, Gianfranco Pacchioni
Summary: In this work, the pH- and facet-dependent surface chemistry of TiO2/water interfaces was studied using ab initio molecular dynamics simulations. Acid-base equilibrium constants were determined at the interface, allowing for estimation of the pH at the point of zero charge, an important experimental observable. The amount of H+, OH-, and adsorbed H2O species on the surfaces was predicted based on simulated equilibrium constants, providing insights into water splitting semi-reactions. The complex morphology of TiO2 particles was approximated by considering different surfaces.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Chemistry, Physical
Sergio Tosoni
Summary: Mn3O4 Hausmannite thin films supported on (Cu, Ag, Au) coinage metals were investigated using DFT calculations. The interface between the films and metal support exhibited different lattice and ionic match, leading to different interactions. The films on Cu (111) and Au (111) weakly adhered due to unfavorable structural match, while strong adhesion was observed on Ag(100) with commensurate lattice and epitaxial growth. A negative charge flow from the support to the film was reported, resulting in the reduction of the film and an increase in magnetic moments of metal ions in the octahedral sublattice. The ferrimagnetic ordering varied in supported films exposing different crystal faces.
APPLIED SURFACE SCIENCE
(2023)
Article
Chemistry, Multidisciplinary
Alexander Fuhrich, Joachim Paier, Sergio Tosoni, Adrian Leandro Lewandowski, Leonard Gura, Wolf-Dieter Schneider, Gianfranco Pacchioni, Hans-Joachim Freund
Summary: Two-dimensional oxide films, including silica, germania, and mixed silica-germania films, supported on a Ru(0001) single crystal surface were studied. The modification of the properties of silica films through the incorporation of germanium atoms was investigated. X-ray photoelectron spectroscopy in combination with LEED and I/V LEEM measurements were used to judge the formation of mixed films.
ISRAEL JOURNAL OF CHEMISTRY
(2023)
Article
Chemistry, Physical
Tilak Das, Sergio Tosoni
Summary: A self-consistent Hubbard-U search was conducted on the bulk honeycomb layered oxide SrRu2O6 for potential applications as Li and post-Li battery cathode materials. The study employed first-principles density functional theory (DFT) based calculations and analysis. The results revealed that intercalation of Li, Ca, and Al metals did not affect the SRO magnetic ordering. The host SRO showed a quenched magnetic moment after intercalation, indicating the transfer of electrons to neighboring Ru sublattices.
SOLID STATE IONICS
(2023)
Review
Chemistry, Physical
Giovanni Di Liberto, Ilaria Barlocco, Livia Giordano, Sergio Tosoni, Gianfranco Pacchioni
Summary: This article discusses several fundamental elements required for successful computational modeling of single-atom catalysts (SACs) for electrocatalytic applications, including the role of the adopted exchange-correlation functional within a given DFT approach and the role of the local coordination of the active transition metal atom. Next, it explores new intermediates that can form on SACs, which are not present on extended metal electrodes, and how to model solvation, with a focus on the dual role of water as both a solvent and a ligand on SACs. Finally, challenges related to the inclusion of pH and voltage in models and some open issues concerning the rational design of new SACs are discussed.
CURRENT OPINION IN ELECTROCHEMISTRY
(2023)
Article
Chemistry, Physical
Ilaria Barlocco, Giovanni Di Liberto, Gianfranco Pacchioni
Summary: Single Atom Catalysts (SACs) bridge the gap between homogenous and heterogenous catalysis and show promise in various chemical reactions, including water splitting. This study focuses on SACs embedded in Covalent Organic Frameworks (COFs) and investigates their reactivity in Hydrogen and Oxygen Evolution Reactions (HER and OER, respectively) using density functional theory (DFT). The results reveal the formation of unique intermediates and shed light on the reaction mechanism, providing valuable insights for the design of novel catalytic materials.
Article
Chemistry, Multidisciplinary
Giovanni Di Liberto, Sergio Tosoni, Luis A. Cipriano, Gianfranco Pacchioni
Summary: Single-atom catalysis is a highly investigated topic in the catalytic community, offering advantages such as the use of minimal precious metals, higher selectivity, and bridging homogeneous and heterogeneous catalysis. The combination of advanced characterization techniques and theoretical calculations can provide a conceptual framework to better understand structure-function relationships.
ACCOUNTS OF MATERIALS RESEARCH
(2022)
Article
Chemistry, Multidisciplinary
Saeed Sovizi, Sergio Tosoni, Robert Szoszkiewicz
Summary: Sub-nanometer MoOx clusters were found on the basal planes of 2H MoS2 crystals during thermal oxidative etching at 370 degrees C. These clusters were predominantly composed of single MoO3 molecules and their dimers at sulfur vacancies, as observed using high resolution non-contact atomic force microscopy. Additional spectroscopic and microscopy techniques confirmed the sparse coverage of MoO3/MoOx species on the MoS2 surface. The findings support the previously proposed stoichiometry of oxidative etching.
NANOSCALE ADVANCES
(2022)
Article
Chemistry, Physical
Farahnaz Maleki, Gianfranco Pacchioni
Summary: The characterization of catalytic oxide surfaces is often done by studying the properties of adsorbed probe molecules. In this study, DFT+D calculations were performed to investigate the adsorption properties of trimethylphosphine (TMP) on different oxide surfaces. The aim was to identify trends or patterns that can help correlate the P-31 chemical shift with physico-chemical properties of the oxide surfaces. The results showed that a simple correlation can be found between the P-31 chemical shift and adsorption energy within the same oxide.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Sergio Tosoni, Gianfranco Pacchioni
Summary: This study investigates the magnetic ground state and hyperfine coupling parameters of first-row transition metal atoms adsorbed on ultrathin insulating oxide films using DFT calculations. The results highlight the challenges in calculating hyperfine coupling constants and the dependence on the magnetic state and electron configuration of the metal atoms. The role of the metal support is also emphasized, as it can significantly influence the hyperfine coupling constants and have important implications for applications in quantum technologies or memory devices.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)