Atomic Structure Research Articles

Restoring the electronic properties of epitaxial graphene on SiC substrate by Ar intercalation

Thermal decomposition of 6H-SiC(0001) under an argon atmosphere is a promising technique to fabricate large-scale epitaxial graphene monolayers for electronic applications. In this manuscript, we report on the intercalation of argon, hydrogen and oxygen atoms underneath a graphene buffer layer (BL) on SiC(0001), involving bond formation between the intercalated agent and Si atoms. Density Functional Theory calculations were performed to investigate the atomic structure, stability and electronic properties of quasi free-standing monolayer graphene and bilayer graphene, accomplished by intercalation. According to our results, as the Ar intercalated atoms saturate the silicon dangling bonds in the upper SiC surface, the BL is completely detached from the substrate and transformed into free-standing graphene. Ar intercalation would be hindered by the concurrent and thermodynamically more spontaneous adsorption of Ar atop the graphene layers, resulting in a pronounced decrease of the process efficiency. High Ar-coverage regimes and low kinetic barriers for Ar intercalation might shift the intercalation/adsorption balance. These factors as well as strategies such as ion implantation could be explored to identify more favorable conditions to experimentally test Ar intercalation as a simple method to achieve control of the electronic properties of the BL and help preserve the unique characteristics of graphene.

Tunneling Proton Grotthuss Transfer Channels by Hydrophilic-Zincophobic Heterointerface Shielding for High-Performance Zn-MnO2 Batteries.

Hollandite-type manganese dioxide (α-MnO2) is recognized as a promising cathode material upon high-performance aqueous zinc-ion batteries (ZIBs) owing to the high theoretical capacities, high working potentials, unique Zn2+/H+ co-insertion chemistry, and environmental friendliness. However, its practical applications limited by Zn2+ accommodation, where the strong coulombic interaction and sluggish kinetics cause significant lattice deformation, fast capacity degradation, insufficient rate capability, and undesired interface degradation. It remains challenging to accurately modulate H+ intercalation while suppressing Zn2+ insertion for better lattice stability and electrochemical kinetics. Herein, proton Grotthuss transfer channels are first tunneled by shielding MnO2 with hydrophilic-zincophobic heterointerface, fulfilling the H+-dominating diffusion with the state-of-the-art ZIBs performance. Local atomic structure and theoretical simulation confirm that surface-engineered α-MnO2 affords to the synergy of Mn electron t2g-eg activation, oxygen vacancy enrichment, selective H+ Grotthuss transfer, and accelerated desolvation kinetics. Consequently, fortified α-MnO2 achieves prominent low current density cycle stability (≈100% capacity retention at 1C after 400 cycles), remarkable long-lifespan cycling performance (98% capacity retention at 20C after 12000 cycles), and ultrafast rate performance (up to 30C). The study exemplifies a new approach of heterointerface engineering for regulation of H+-dominating Grotthuss transfer and lattice stabilization in α-MnO2 toward reliable ZIBs.

Unveiling Variations in Electronic and Atomic Structures Due to Nanoscale Wurtzite and Zinc Blende Phase Separation in GaAs Nanowires.

Phase separation is an intriguing phenomenon often found in III-V nanostructures, but its effect on the atomic and electronic structures of III-V nanomaterials is still not fully understood. Here we study the variations in atomic arrangement and band structure due to the coexistence of wurtzite (WZ) and zinc blende (ZB) phases in single GaAs nanowires by using scanning transmission electron microscopy and monochromated electron energy loss spectroscopy. The WZ lattice distances are found to be larger (by ∼1%), along both the nanowire length direction and the perpendicular direction, than the ZB lattice. The band gap of the WZ phase is ∼20 meV smaller than that of the ZB phase. A shift of ∼70 meV in the conduction band edge between the two phases is also found. The direct and local measurements in single GaAs nanowires reveal important effects of phase separation on the properties of individual III-V nanostructures.

Comparative study on physical properties of bio-based PA56 fibers and wearability of their fabrics

Abstract Bio-based polyamide 56 (PA56) has significant advantages in reducing oil dependence and reducing carbon emissions. This study compared the physical properties of bio-based PA56 and conventional polyamide 66 (PA66) fibers and their fabrics. The results showed that due to the odd arrangement structure of carbon atoms in PA56 fiber molecules, its crystallinity and orientation were lower than those of PA66. At the same time, PA56 had a higher degradation rate and coloring rate due to its smaller crystallinity and higher moisture content and gave PA56 fabrics better instantaneous cooling and moisture absorption and drying properties. In addition, the molecular structure characteristics of PA56 also lead to a lower stiffness and soft feel of the fabric, which is beneficial for improving the curling phenomenon of the fabric. Overall, bio-based PA56 fibers can meet the applications in the textile and clothing field and can largely replace PA66, which is worthy of further research and utilization.

Application of the tight-binding method onto the Von Neumann equation

AbstractThis paper presents a numerical framework for the analysis of quantum devices based on the Von Neumann (VN) equation, which involves the concept of the Tight-Binding Method (TBM). The model is based on the application of the Tight-Binding Hamiltonian within Quantum Liouville Type Equations and has the advantage that the atomic structure of the materials used is taken into account. Furthermore, the influence of a Complex Absorbing Potential (CAP) as a complementary boundary condition and its essential contribution to the system stability with respect to the eigenvalue spectrum is discussed.

Atomically Resolved Phase Coexistence in VO2 Thin Films.

Concurrent structural and electronic transformations in VO2 thin films are of 2-fold importance: enabling fine-tuning of the emergent electrical properties in functional devices, yet creating an intricate interfacial domain structure of transitional phases. Despite the importance of understanding the structure of VO2 thin films, a detailed real-space atomic structure analysis in which the oxygen atomic columns are also resolved is lacking. Moreover, intermediate atomic structures have remained elusive due to the lack of robust atomically resolved quantitative analysis. Here, we directly resolve both V and O atomic columns and discover the presence of intermediate monoclinic (M2) phase nanolayers (less than 2 nm thick) in epitaxially grown VO2 films on a TiO2 (001) substrate, where the dominant part of VO2 undergoes a transition from the tetragonal (rutile) phase to the monoclinic M1 phase. Strain analysis suggests that the presence of the M2 phase is related to local strain gradients near the TiO2/VO2 interface. We unfold the crucial role of imaging the spatial configurations of the oxygen anions (in addition to V cations) by utilizing atomic-resolution electron microscopy. Our approach can be used to unravel the structural transitions in a wide range of correlated oxides, offering substantial implications for, e.g., optoelectronics and ferroelectrics.

NiS ultrafine nanorod with translational and rotational symmetry

Abstract Anisotropy is a significant and prevalent characteristic of materials, conferring orientation-dependent properties, meaning that the creation of original symmetry enables the key functionality that is not found in nature. Even with the advancements in atomic machining, synthesis of separated symmetry in different directions within a single structure remains an extraordinary challenge. Here, we successfully fabricate NiS ultrafine nanorods with separated symmetry along two directions. The atomic structure of the nanorod exhibits rotational symmetry in the radial direction, while its axial direction is characterized by divergent translational symmetry, surpassing the conventional crystalline structures known to date. It does not fit the traditional description of the space group and the point group in three dimensions, so we define it as a new structure in which translational symmetry and rotational symmetry are separated. Further corroborating the atomic symmetric separation in the electronic structure, we observed the combination of stripe and vortex magnetic domains in a single nanorod with different directions, in accordance with the atomic structure. The manipulation of nanostructure at the atomic level introduces a novel approach to regulate new properties finely, leading to the proposal of new nanotechnology mechanisms.

Improvement on electrochemiluminescence properties of graphite carbon nitride by metal oxidation state regulation

AbstractReasonable design is of great significance for improving the performance of electrochemiluminescence (ECL) co‐reactant accelerators. The different d‐band structure of metal single atoms will produce different oxidation states, which may change the adsorption of reaction intermediates to the catalyst and affect its catalytic activity. In this study, we have demonstrated that the ECL performances of graphite carbon nitride (CN) can be promoted by modulating the metal oxidation states of co‐reaction accelerator for the first time. The oxidation states of Au were modulated by the different electronic metal–support interaction (EMSI) between the co‐reaction accelerator (Au single atoms, Au nanoparticles [Au NPs]) and CN, and the effects of Au oxidation states on the ECL performances of CN were investigated. Comparison to pristine CN and CN nanosheets supported Au nanoparticles (Au NPs/CN), stronger and more stable ECL intensity of CN nanosheets supported Au single‐atoms (AuS/CN) was obtained. The ECL signal of AuS/CN was about 32.2 times that of the original CN, and 2.8 times that of Au NPs/CN in the same Au loading content (0.8%). Detailed mechanism revealed that AuS/CN with higher Au oxidation state has better conductivity and stronger catalytic activity, which promotes the electric reduction of CN and S2O82−, increases the lifetime of the excited state CN*, and significantly improves the ECL performance of CN. In addition, this work provides a detailed understanding of the essence of EMSI for the ECL intensity amplification and established a feasible method for the improvement of ECL capacities of co‐reactant accelerators.

Experiment-Driven Atomistic Materials Modeling: A Case Study Combining X-Ray Photoelectron Spectroscopy and Machine Learning Potentials to Infer the Structure of Oxygen-Rich Amorphous Carbon.

An important yet challenging aspect of atomistic materials modeling is reconciling experimental and computational results. Conventional approaches involve generating numerous configurations through molecular dynamics or Monte Carlo structure optimization and selecting the one with the closest match to experiment. However, this inefficient process is not guaranteed to succeed. We introduce a general method to combine atomistic machine learning (ML) with experimental observables that produces atomistic structures compatible with experiment by design. We use this approach in combination with grand-canonical Monte Carlo within a modified Hamiltonian formalism, to generate configurations that agree with experimental data and are chemically sound (low in energy). We apply our approach to understand the atomistic structure of oxygenated amorphous carbon (a-COx), an intriguing carbon-based material, to answer the question of how much oxygen can be added to carbon before it fully decomposes into CO and CO2. Utilizing an ML-based X-ray photoelectron spectroscopy (XPS) model trained from GW and density functional theory (DFT) data, in conjunction with an ML interatomic potential, we identify a-COx structures compliant with experimental XPS predictions that are also energetically favorable with respect to DFT. Employing a network analysis, we accurately deconvolve the XPS spectrum into motif contributions, both revealing the inaccuracies inherent to experimental XPS interpretation and granting us atomistic insight into the structure of a-COx. This method generalizes to multiple experimental observables and allows for the elucidation of the atomistic structure of materials directly from experimental data, thereby enabling experiment-driven materials modeling with a degree of realism previously out of reach.

The heavy atom structure, "cis effect" on methyl internal rotation, and 14N nuclear quadrupole coupling of 1-cyanopropene from quantum chemical and microwave spectroscopic analysis.

The microwave spectrum of 1-cyanopropene (crotonitrile) was remeasured using two pulsed molecular jet Fourier transform microwave spectrometers operating from 2.0 to 40.0 GHz. The molecule exists in two isomer forms, E and Z, with respect to the orientation between the methyl and the cyano groups. The spectrum of the Z isomer is more intense. Due to internal rotation of the methyl group, doublets containing A and E torsional species were found for all rotational transitions. Hyperfine splittings arising from the 14N nuclear quadrupole coupling were resolved. The heavy atom structure of the Z isomer was determined by observation of 13C and 15N isotopologue spectra in natural abundances. The experimental results were supported by quantum chemistry. The complex spectral patterns were analyzed and fitted globally, and the barriers to methyl internal rotation are determined to be 478.325(28) cm-1 and 674.632(76) cm-1 for the Z and E isomers, respectively. The non-bonded intramolecular electrostatic attraction between the methyl group and the 1-cyano substituent overcomes steric hindrance, leading to higher stability of the Z isomer. The consequence is a slight opening of 3.2° of the C(1)-C(2)-C(3) angle and a radical decrease of the methyl torsional barrier in the Z isomer due to steric repulsion.

Study on structure and viscosity evolution mechanism of titanium-containing iron liquid in full viscosity range

This study aims to investigate the relationship between the viscosity of Fe-4.5wt%C-0.2wt%Ti melt and its liquid structure. The actual experimental results of viscosity measurement reveal that the viscosity range of Fe-4.5wt%C-0.2wt%Ti melt can be segmented into three intervals. Through thermodynamically calculated equilibrium phases and high-temperature confocal experiments, it is observed that the abrupt change in viscosity in the lower temperature range is attributed to the precipitation of the graphite phase. Moreover, differential scanning calorimetry experiments exhibit a distinct phase transition in the liquid phase region. To delve into the atomic structure of the liquid phase region, molecular dynamics simulations are employed. The high-temperature liquid structure of Fe-4.5wt%C-0.2wt%Ti melt predominantly consists of vacancies, atomic clusters with Ti as the core, and atomic clusters with C as the core. Within the high-temperature liquid phase region, the conversion of Free-Fe and C1-Fe to Cx-Fe occurs, resulting in a reduction of free volume and enhanced stability of the cluster. Consequently, the inhomogeneity of the Fe-4.5wt%C-0.2wt%Ti melt increases, and the viscosity exhibits a significant increase with temperature, leading to a variation in the viscosity within the liquid phase interval.

Constructing Single-Atom Active Sites Embedded in Hexagonal Boron Nitride for Adsorption and Sensing of Lithium Battery Thermal Runaway Gases.

The utilization and selectivity of single atoms have garnered significant attention among researchers. However, they are easy to agglomerate because of their high surface energy. To overcome this challenge, it is crucial to seek suitable carriers to anchor single metal atoms to achieve optimal performance. In this work, the structures of transition metal single atoms embedded in hexagonal boron nitride (MB2N2, M = Fe, Co, Ni, Cu, Zn) are constructed and used for the adsorption and sensing of lithium battery thermal runaway gases (H2, CO, CO2, CH4) through the DFT method. The adsorption behavior of MB2N2 was evaluated through the adsorption energy, sensitivity, and recovery time. The calculation results indicate that CoB2N2 exhibits strong adsorption capacity for both H2 and CO. The sensitivity of FeB2N2 toward CO is as high as 3.232 × 1016. Subsequently, the adsorption mechanism was studied through TDOS and PDOS, and the results showed that hybridization between orbitals enhanced the gas adsorption performance. This study presents novel approaches for designing single-atom carriers and developing MB2N2 sensors for detecting lithium battery thermal runaway gases.

Phase‐Controlled Synthesis of Large‐Area Trigonal 2D Cr2S3 Thin Films via Ultralow Gas‐Flow Governed Dynamic Transport

AbstractAs for nonlayered 2D polymorphic materials, especially for Cr‐based chalcogenides, large‐area thin film growth with phase control is considered the most important synthesis challenge for magnetic, electronic, and optoelectronic devices. However, the synthesis methods of large continuous thin films for nonlayered 2D materials are still limited and rarely reported, also for the phase control growth, which is inhibited by isotropic 3D growth and similar Gibbs free energy for different phases. Herein, enhanced mass transport chemical vapor deposition is established to achieve the control synthesis of trigonal Cr2S3 thin films, in which the stable boundary layer supplies the continuous reaction species and tunes the reaction kinetics. The trigonal phase formation is confirmed by atomic structure characterization, optical absorption and piezoelectric measurements, demonstrating unique physical properties different from rhombohedral phase. The trigonal Cr2S3 thin films show obvious layer independent and dissimilar angle‐resolved harmonic generation, indicating the surface broken symmetry that can be understood by the combination of negligible piezoelectric response for bulk. The work presents the large‐area synthesized strategy by the modification of mass transport for nonlayered 2D materials with new phase formation and establishes the surface symmetry breaking dominated SHG mechanism for future nonlinear optical materials.

Decoding Active Sites for Highly Efficient Semihydrogenation of Acetylene in Palladium-Copper Nanoalloys.

Accurately decoding the three-dimensional atomic structure of surface active sites is essential yet challenging for a rational catalyst design. Here, we used comprehensive techniques combining the pair distribution function and reverse Monte Carlo simulation to reveal the surficial distribution of Pd active sites and adjacent coordination environment in palladium-copper nanoalloys. After the fine-tuning of the atomic arrangement, excellent catalytic performance with 98% ethylene selectivity at complete acetylene conversion was obtained in the Pd34Cu66 nanocatalysts, outperforming most of the reported advanced catalysts. The quantitative deciphering shows a large number of active sites with a Pd-Pd coordination number of 3 distributed on the surface of Pd34Cu66 nanoalloys, which play a decisive role in highly efficient semihydrogenation. This finding not only opens the way for guiding the precise design of bimetal nanocatalysts from atomic-level insight but also provides a method to resolve the spatial structure of active sites.

Crystal Facet Controlled Metal-Support Interaction in Uricase Mimics for Highly Efficient Hyperuricemia Treatment.

The effect of strong metal-support interaction (SMSI) has never been systematically studied in the field of nanozyme-based catalysis before. Herein, by coupling two different Pd crystal facets with MnO2, i.e., (100) by Pd cube (Pdc) and (111) by Pd icosahedron (Pdi), we observed the reconstruction of Pd atomic structure within the Pd-MnO2 interface, with the reconstructed Pdc (100) facet more disordered than Pdi (111), verifying the existence of SMSI in such coupled system. The rearranged Pd atoms in the interface resulted in enhanced uricase-like catalytic activity, with Pdc@MnO2 demonstrating the best catalytic performance. Theoretical calculations suggested that a more disordered Pd interface led to stronger interactions with intermediates during the uricolytic process. In vitro cell experiments and in vivo therapy results demonstrated excellent biocompatibility, therapeutic effect, and biosafety for their potential hyperuricemia treatment. Our work provides a brand-new perspective for the design of highly efficient uricase-mimic catalysts.

Scalable Customization of Crystallographic Plane Controllable Lithium Metal Anodes for Ultralong-Lasting Lithium Metal Batteries.

A formidable challenge to achieve the practical applications of rechargeable lithium (Li) metal batteries (RLMBs) is to suppress the uncontrollable growth of Li dendrites. One of the most effective solutions is to fabricate Li metal anodes with specific crystal plane, but still lack of a simple and high-efficient approach. Herein, a facile and controllable way for the scalable customization of polished Li metal anodes with highly preferred (110) and (200) crystallographic orientation (donating as polished Li(110) and polished Li(200), respectively) by regulating the times of accumulative roll bonding, is reported. According to the inherent characteristics of polished Li(110)/Li(200), the influence of Li atomic structure on the electrochemical performance of RLMBs is deeply elucidated by combining theoretical calculations with relative experimental proofs. In particular, a polished Li(110) crystal plane is demonstrated to induce Li+ uniform deposition, promoting the formation of flat and dense Li deposits. Impressively, the polished Li(110)||LiFePO4 full cells exhibit unprecedented cycling stability with 10000 cycles at 10 C almost without capacity degradation, indicating the great potential application prospect of such textured Li metal. More valuably, this work provides an important reference for low-cost, continued, and large-scale production of Li metal anodes with highly preferred crystal orientation through roll-to-roll manufacturability.

Single‐element amorphous metals

AbstractTo unveil the nature of amorphous states, single‐element amorphous metals have been the perfect research subject due to the simplest composition. However, the extreme crystal nucleation and growth rate in single‐element metal make the synthesis of single‐element amorphous metals seemingly impossible in the past. Fortunately, benefited by several delicate synthetic strategies developed recently, the single‐element amorphous metals have been successfully demonstrated. This review aims to provide a systematic overview of the synthesis of single‐element amorphous metals covering the challenges in physics and recent achievements. In addition, current understanding of the atomic and electronic structures of single‐element amorphous metal has also been included. Finally, the challenges that worth further investigation are discussed. By identifying the potential avenues for further exploration, this review aims to contribute valuable insights that will propel the cognition of single‐element amorphous metals.

Wall-crossing effects on quiver BPS algebras

BPS states in supersymmetric theories can admit additional algebro-geometric structures in their spectra, described as quiver Yangian algebras. Equivariant fixed points on the quiver variety are interpreted as vectors populating a representation module, and matrix elements for the generators are then defined as Duistermaat-Heckman integrals in the vicinity of these points. The well-known wall-crossing phenomena are that the fixed point spectrum establishes a dependence on the stability (Fayet-Illiopolous) parameters ζ, jumping abruptly across the walls of marginal stability, which divide the ζ-space into a collection of stability chambers — “phases” of the theory. The standard construction of the quiver Yangian algebra relies heavily on the molten crystal model, valid in a sole cyclic chamber where all the ζ-parameters have the same sign. We propose to lift this restriction and investigate the effects of the wall-crossing phenomena on the quiver Yangian algebra and its representations — starting with the example of affine super-Yangian \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{Y}}\\left({\\widehat{\\mathfrak{g}\\mathfrak{l}}}_{1\\left|1\\right.}\\right)$$\\end{document}. In addition to the molten crystal construction more general atomic structures appear, in other non-cyclic phases (chambers of the ζ-space). We call them glasses and also divide in a few different classes. For some of the new phases we manage to associate an algebraic structure again as a representation of the same affine Yangian \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{Y}}\\left({\\widehat{\\mathfrak{g}\\mathfrak{l}}}_{1\\left|1\\right.}\\right)$$\\end{document}. This observation supports an earlier conjecture that the BPS algebraic structures can be considered as new wall-crossing invariants.

Crystallography applications: A comprehensive review

Crystallography is an essential scientific technique profoundly influencing our understanding of atomic and molecular structures in materials, providing insights into the arrangement and interactions of atoms. This review highlights crystallographys extensive applications across chemistry, biology, physics, and materials science, emphasizing its critical role and adaptability. The paper traces crystallographys historical development, outlines its fundamental principles, and celebrates its significant milestones and contributions to science. By revealing the complex structures and functions of compounds, from simple molecules to complex macromolecules, crystallography has catalyzed advancements in drug development, material innovation, and fundamental scientific understanding. The paper asserts crystallographys continued prominence in scientific research, with its application and influence steadily growing. Its pivotal in enhancing our understanding of matter, driving technological and material advancements, and offering solutions to complex scientific questions. Moreover, the review addresses the current challenges and future directions of crystallography, pointing out potential areas for innovation and improvement. As technology advances, crystallographys significance in various scientific disciplines remains indispensable, solidifying its position as a cornerstone of scientific inquiry and discovery. The paper concludes by reinforcing the techniques vital role in pushing the boundaries of science and technology.

Strong-field photoelectron holography in the subcycle limit

Strong-field photoelectron holography is promising for the study of electron dynamics and structure in atoms and molecules, with superior spatiotemporal resolution compared to conventional electron and X-ray diffractometry. However, the application of strong-field photoelectron holography has been hindered by inter-cycle interference from multicycle fields. Here, we address this challenge by employing a near-single-cycle field to suppress the inter-cycle interference. We observed and separated two distinct holographic patterns for the first time. Our measurements allow us not only to identify the Gouy phase effect on electron wavepackets and holographic patterns but also to correctly extract the internuclear separation of the target molecule from the holographic pattern. Our work leads to a leap jump from theory to application in the field of strong-field photoelectron holography-based ultrafast imaging of molecular structures.