Structural Distortion Research Articles

Devising an edge effect compensation procedure to eliminate structural distortions during frequency filtering

The object of this study is the process of filtering astronomical frames that contain images of potential objects in the Solar System. To recognize the image of each such object in contrast with the background of the frame, it is necessary to carry out frequency filtering of the image. Any frequency filtering using various image filters is aimed at reducing the dynamic range of the background substrate. Also, frequency filtering leads to an increase in the signal-to-noise ratio of the entire image or its fragments, depending on the configuration. However, the identified problem area of each image during frequency filtering is the distortion of the structure of its edges. Therefore, to solve this problem, an edge effect compensation procedure has been proposed to eliminate structural distortions during frequency filtering. Complementing the image with borders on all sides and the augmented extended image made it possible to introduce a formal connection between the pixel values of the extended image fragment and the pixel values of the extended original image. Testing was carried out using a high-pass Gaussian filter. The use of the devised edge effect compensation procedure made it possible to remove distortion of the structure of the image edges. The devised edge effect compensation procedure was tested in practice within the CoLiTec project. It was implemented during the in-frame processing stage of the Lemur software. The study showed that the use of the devised edge effect compensation procedure makes it possible to remove image artifacts compared to conventional filtering without taking into account the edge effect. Also, owing to edge effect compensation, structural image distortions were eliminated, and the signal-to-noise ratio was increased by 7–10 times

Interfacial stability and electronic properties of YBCO/ABO3 heterostructures: A comparative DFT study

In this study, we utilized density functional theory (DFT) to analyze the interfacial properties of YBa2Cu3O7 (YBCO) with perovskite metal oxides LaAlO3 (LAO), KTaO3 (KTO), and SrTiO3 (STO). We focused on surface energies, lattice mismatches, strain energies, and adhesion energies to gauge the stability and compatibility of these interfaces. Our findings indicate that KTO exhibits the highest surface preference due to its lowest surface energy (0.054 eV/Å 2), suggesting superior surface stability. Moreover, LAO and STO show minor lattice mismatches with YBCO, implying effective interface integration, while YBCO/KTO interfaces experience significant strain due to extensive lattice mismatches. STO is distinguished by the lowest strain energy (0.07 eV), indicating minimal energy requirement for lattice mismatch accommodation, unlike KTO, which demonstrates high strain energy (0.42 eV) and potential structural distortions. The strongest interfacial bond, as indicated by an adhesion energy of −2.16 eV, was observed at YBCO/LAO, while the weakest was found at the YBCO/KTO interface, with an adhesion energy of −0.56 eV. Additionally, charge density difference (CDD) analysis highlighted electron density redistribution at the interfaces, predominantly around interfacial oxygen atoms, indicating a mix of ionic and covalent bonding. This study provides comparative insights into the interfacial characteristics of YBCO/ABO3 heterostructures, suggesting pathways for optimizing their design and performance.

Synthesis of Samarium Nitride Thin Films on Magnesium Oxide (001) Substrates Using Molecular Beam Epitaxy

Rare-earth nitrides are an exciting family of materials with a wide variety of properties desirable for new physics and applications in spintronics and superconducting devices. Among them, samarium nitride is an interesting compound reported to have ferromagnetic behavior coupled with the potential existence of p-wave superconductivity. Synthesis of high-quality thin films is essential in order to manifest these behaviors and understand the impact that vacancies, structural distortions, and doping can have on these properties. In this study, we report the synthesis of samarium nitride monocrystalline thin films on magnesium oxide (001) substrates with a chromium nitride capping layer using molecular beam epitaxy (MBE). We observed a high-quality monocrystalline SmN film with matching orientation to the substrate, then optimized the growth temperature. Despite the initial 2 nm of growth showing formation of a potential samarium oxide layer, the subsequent layers showed high-quality SmN, with semiconducting behavior revealed by an increase in resistivity with decreasing temperature. These promising results highlight the importance of studying diverse heteroepitaxial schemes and open the door for integration of rare-earth nitrides and transition metal nitrides for future spintronic devices.

Proton Intercalation into an Open-Tunnel Bronze Phase with Near-Zero Volume Change.

Managing safety and supply-chain risks associated with lithium-ion batteries (LIBs) is an urgent task for sustainable development. Aqueous proton batteries are attractive alternatives to LIBs because using water and protons addresses these two risks. However, most host materials undergo large volume changes upon H+ intercalation, which induces intraparticle cracking to accelerates parasitic reactions. Herein, we report that Mo3Nb2O14 bronze exhibits reversible H+ intercalation (200 mAh g-1) with a Coulombic efficiency of 99.7% owing to near-zero volume change and solid-solution-type phase transition. Combination of experimental and theoretical analyses clarifies that rotation and shrinkage of open tunnels, which consist of flexible corner-sharing Mo/NbOn polyhedra, relieve local structural distortions upon H+ intercalation to suppress intraparticle cracking. The prototype full cell of an aqueous proton battery with a Mo3Nb2O14 anode operates stably over 1000 charge/discharge cycles. This study reveals the importance of implementing distortion-relieving voids in host materials to reduce volume change upon charge/discharge.

Engineering a vanadium-incorporated MoS2-based mixed metal dichalcogenide system for improved supercapacitor performance

In this study, we developed a mixed metal dichalcogenide system of molybdenum‑vanadium disulfide with the chemical formula Mo1-xVxS2, where x = 0.3, 0.5, and 0.7, corresponding to Mo:V ratios of 70:30, 50:50, and 30:70 using a facile one-pot hydrothermal method. This mixed metal structure is expected to influence both the basal plane and the edge plane towards engineering the active sites in the resulting system forming xMon+-yV4+-zS2− network, which is a crucial for its improved electrochemical performance. Structural studies confirmed the emergence of structural distortion in the system due to the difference in the ionic sizes of Mo and V ions, leading to strain in the lattices. Furthermore, electron microscopic analysis revealed the formation of aggregated nano-petals for bare MoS2, while these petals self-assembled to form flower-like microspheres upon the introduction of V in the mixed metal (Mo1-xVxS2) systems. Consequently, the Mo0.5V0.5S2 delivered a specific capacitance of 492.2 F g−1 at 1 A g−1 with substantial capacitance retention of 94 % up to 3000 cycles, which is twofold higher compared to bare MoS2. Moreover, the fabricated symmetric device achieved an energy density of 19.5 Wh kg−1 and a maximum power density of 9000 W kg−1 with capacitance retention of 92.8 and 86.3 % after 5000 and 10,000 charge/discharge cycles, respectively.

Surface Doping and Dual Nature of the Band Gap in Excitonic Insulator Ta2NiSe5.

Excitons in semiconductors and molecules are widely utilized in photovoltaics and optoelectronics, and high-temperature coherent quantum states of excitons can be realized in artificial electron-hole bilayers and an exotic material of an excitonic insulator (EI). Here, we investigate the band gap evolution of a putative high-temperature EI Ta2NiSe5 upon surface doing by alkali adsorbates with angle-resolved photoemission and density functional theory (DFT) calculations. The conduction band of Ta2NiSe5 is filled by the charge transfer from alkali adsorbates, and the band gap decreases drastically upon the increase of metallic electron density. Our DFT calculation, however, reveals that there exist both structural and excitonic contributions to the band gap tuned. While electron doping reduces the band gap substantially, it alone is not enough to close the band gap. In contrast, the structural distortion induced by the alkali adsorbate plays a critical role in the gap closure. This work indicates a combined electronic and structural nature for the EI phase of the present system and the complexity of surface doping beyond charge transfer.

Effects of doping with magnetic cations on the hybrid improper ferroelectricity in Sr3Sn2O7

We here report the structural, magnetic and electrical properties of Sr2.9La0.1Sn1.9M0.1O7 (M= Cr, Mn or Fe) compounds. This La/M codoping of the hybrid improper ferroelectric Sr3Sn2O7, allows introducing magnetic cations into the perovskite layers of this Ruddlesden-Popper phase. The doping induces minor structural changes, preserving the polar structure with space group A21am of the undoped compound. The perovskite tolerance factor of all doped samples is slightly lower than in Sr3Sn2O7, which preserves the tilts and rotations of SnO6 octahedra. Doped samples exhibit a paramagnetic behavior down to 5 K and obey the Curie-Weiss law above 200 K. The effective paramagnetic moments agree with the expected spin-only values of the respective magnetic M3+ cations. All samples show a ferroelectric hysteresis loop at room temperature, but the doped samples show larger coercive fields. Additionally, the doping with magnetic cations has important effects on the dielectric properties: a strong decrease of the temperature of the ferroelectric transition together with a smoothing of the anomaly in the dielectric permittivity. These results suggest that the disorder produced by the two aliovalent substitutions is detrimental for the ferroelectric properties due to point charge defects but, at the same time, the prevalence of the structural distortion (tilts and rotations) preserves the ferroelectricity in the investigated doping regime.

Structure Distortion Endows Copper Nanoclusters with Surface-Active Uncoordinated Sites for Boosting Catalysis.

The utilization of structure distortion to modulate the electronic structure and alter catalytic properties of metallic nanomaterials is a well-established practice, but accurately identifying and comprehensively understanding these distortions present significant challenges. Ligand-stabilized metal nanoclusters with well-defined structures serve as exemplary model systems to illustrate the structure chemistry of nanomaterials, among which few studies have investigated nanocluster models that incorporate structural distortions. In this work, a novel copper hydride nanocluster, Cu42(PPh3)8(RS)4(CF3COO)10(CH3O)4H10 (Cu42; PPh3 is triphenylphosphine and RSH is 2,4-dichlorophenylthiol), with a highly twisted structure has been synthesized in a simple way. Structural analysis reveals Cu42 comprises two Cu25 units that are conjoined in a nearly orthogonal manner. The dramatic distortion in the metal framework, which is driven by multiple interactions from the surface ligands, endows the cluster with a rich array of uncoordinated metal sites on the surface. The resulting cluster, as envisioned, exhibits remarkable activity in catalyzing carbonylation of anilines. The findings from this study not only provides atomically precise insights into the structural distortions that are pertinent to nanoparticle catalysts but also underscores the potential of structurally distorted NCs as a burgeoning generation of catalysts with precise structures and outstanding performances that can be tailored for specific functions.

Boosting the Sodium‐Ion Storage Performance of Prussian Blue Analogs by Crystalline Regulation

AbstractIn the development of practical sodium‐ion batteries, electrochemical performance and cost efficiency of the electrode materials are vital considerations. Prussian blue analogs (PBAs) have emerged as promising cathode materials due to their affordability, high theoretical capacity, and cycling stability. However, low crystallinity can negatively impact their performance. This study introduces a straightforward “chelating agent‐assisted” method for producing highly crystalline PBAs. The resulting cathode boasts excellent characteristics, including a high capacity of 150 mAh g−1, an initial Coulombic efficiency of 87.2 %, a long cycling lifespan of 1000 cycles, and superior rate performance. Furthermore, the study shows that the low structure distortion and high sodium diffusion coefficient can be attributed to the suppression of structural defects, as evidenced by in situ synchrotron powder diffraction. We believe these findings have the potential to enable the widespread use of PBAs in sodium‐ion batteries for an affordable and large‐scale energy storage system.

Interplay of kernel shape and surface structure for NIR luminescence in atomically precise gold nanorods

It is challenging to attain strong near-infrared (NIR) emissive gold nanoclusters. Here we show a rod-shaped cluster with the composition of [Au28(p-MBT)14(Hdppa)3](SO3CF3)2 (1 for short, Hdppa is N,N-bis(diphenylphosphino)amine, p-MBT is 4-methylbenzenethiolate) has been synthesized. Single crystal X-ray structural analysis reveals that it has a rod-like face-centered cubic (fcc) Au22 kernel built from two interpenetrating bicapped cuboctahedral Au15 units. 1 features NIR luminescence with an emission maximum at 920 nm, and the photoluminescence quantum yield (PLQY) is 12%, which is 30-fold of [Au21(m-MBT)12(Hdppa)2]SO3CF3 (2, m-MBT is 3-methylbenzenethiolate) with a similar composition and 60-fold of Au30S(S‑t‑Bu)18 with a similar structure. time-dependent DFT(TDDFT)calculations reveal that the luminescence of 1 is associated with the Au22 kernel. The small Stokes shift of 1 indicates that it has a very small excited state structural distortion, leading to high radiative decay rate (kr) probability. The emission of cluster 1 is a mixture of phosphorescence and thermally activated delayed fluorescence(TADF), and the enhancement of the NIR emission is mainly due to the promotion of kr rather than the inhibition of knr. This work demonstrates that the metal kernel and the surface structure are both very important for cluster-based NIR luminescence materials.

Effect of Cation Incorporation on the Structural Distortions and Phase Transitions in Mixed Lead Chloride Perovskite Single Crystals

Effect of Cation Incorporation on the Structural Distortions and Phase Transitions in Mixed Lead Chloride Perovskite Single Crystals

Investigation of the Octahedral Network Structure in Formamidinium Lead Bromide Nanocrystals by Low-Dose Scanning Transmission Electron Microscopy.

Metal halide perovskites (MHP) are highly promising semiconductors. In this study, we focus on FAPbBr3 nanocrystals, which are of great interest for green light-emitting diodes. Structural parameters significantly impact the properties of MHPs and are linked to phase instability, which hampers long-term applications. Clearly, there is a need for local and precise characterization techniques at the atomic scale, such as transmission electron microscopy. Because of the high electron beam sensitivity of MHPs, these investigations are extremely challenging. Here, we applied a low-dose method based on four-dimensional scanning transmission electron microscopy. We quantified the observed elongation of the projections of the Br atomic columns, suggesting an alternation in the position of the Br atoms perpendicular to the Pb-Br-Pb bonds. Together with molecular dynamics simulations, these results remarkably reveal local distortions in an on-average cubic structure. Additionally, this study provides an approach to prospectively investigating the fundamental degradation mechanisms of MHPs.

Bio-corrosion behaviors and bio-compatibilities of TiNbZrTa and TiNbZrTaMo high entropy alloys

The bio-corrosion behavior and bio-compatibility of TiNbZrTa and TiNbZrTaMo high entropy alloys (HEAs) are crucial for their efficient maintenance during biological implantation. In this work, TiNbZrTa and TiNbZrTaMo HEAs were successfully prepared via vacuum melting, with a β-type titanium alloy Ti35Nb7Zr5Ta, exhibiting good biocompatibility used as a comparison. Due to the high entropy effect of equal atomic ratios, both TiNbZrTa and TiNbZrTaMo HEAs exhibit body-centered cubic (BCC) structure and lattice distortion compared to the β titanium alloy Ti35Nb7Zr5Ta. Mo elements contribute to the formation of a new BCC phase, resulting in a white matrix rich in Ta and Mo, and a dark second phase rich in Ti, Zr, and Nb. Electrochemical test results at 37 °C shown that TiNbZrTa has a wider and more stable passivation area than TiNbZrTaMo. The XPS results shown that formation of the passive film is related to the main elements added. Ti, Nb, Ta and Mo formed oxides via the solid-liquid interface and migrate inward, while Zr is formed at the passivation film/metal substrate interface and migrates outward, finally forming the layered structure of the passivation film. Additionally, the cytotoxicity test of mouse fiber cells was carried out to evaluate the biocompatibility of the HEAs. The results shown that the cell proliferation rate of TiNbZrTa and TiNbZrTaMo HEAs reached 0 and 1, respectively, with TiNbZrTa exhibiting better biocompatibility, as adding Mo reduced the cell proliferation rate. These findings may provide a method for predicting the bio-corrosion behavior and bio-compatibility of HEAs used for biological implantation.

Unraveling the Role of Structural Topology on Chirality Transfer and Chiroptical Properties in Chiral Germanium Iodides.

Chiral hybrid organic-inorganic metal halides are highly promising chiroptoelectronic materials with potential applications in several fields, such as circularly polarized photodetectors, second-order nonlinear optics, and spin-selective devices. However, the ability of manipulating the chiroptical response and the chirality transfer from the organic ligands require one to shed light on structure-property correlations. Herein, we devised and prepared two novel Ge-based chiral hybrid organic-inorganic metal halides showing a different structural topology, namely, a 1D and a 2D arrangement, but composed of the same chemical building blocks: (R/S-ClMBA)3GeI5 and (R/S-ClMBA)2GeI4. Through a combined experimental and computational investigation on these samples, we discuss the impact of structural dimensionality on chiroptical properties, chirality transfer, and spin-splitting effects; also, we highlight the impact of structural distortions. The approach presented here paves the way for a solid understanding of the factors affecting the properties of chiral metal halides, thus allowing a future wise materials engineering.

Structural Distortion of g-C3N4 Induced by a Schiff Base Reaction for Efficient Photocatalytic H2 Evolution.

Photocatalytic H2 evolution by water splitting is a promising approach to address the challenges of environmental pollution and energy scarcity. Graphitic carbon nitride (g-C3N4) has emerged as a star photocatalyst because of its numerous advantages. To address the limitations of traditional g-C3N4, namely its inadequate visible light response and rapid recombination of photogenerated carriers, we employed a schiff base reaction to synthesize -C=N- doped g-C3N4. The introduction of -C=N- groups at the bridging nitrogen sites induced structural distortion in g-C3N4, facilitating n-π* electronic transitions from the lone pair electrons of nitrogen atom and extending light absorption up to 600 nm. Moreover, the presence of heterogeneous π-conjugated electron distribution effectively traps photogenerated electrons and enhances charge carrier separation. Benefiting from its expanded spectral response range, unique electronic properties, increased specific surface area, the doped g-C3N4 exhibited outstanding photocatalytic H2 evolution performance of 1050.13 μmol/g/h. The value was 5.9 times greater than the pristine g-C3N4.

Local Symmetry Deviation from the Average Structure of MnAs Revealed by Pair Distribution Function.

MnAs is an interesting material due to its magnetocaloric properties, which can be utilized in magnetic refrigeration. However, despite major efforts, its magnetic refrigeration performances in the substituted forms could not be improved compared to the parent MnAs phase. Both small and big box modeling of the pair distribution function of MnAs for the local structure description and powder X-ray diffraction for the average structure reveal an inherent local orthorhombic distortion in the hexagonal structure of MnAs. As a result of this distortion, any modification to the hexagonal structure results in an orthorhombic structure and a weaker magnetocaloric performance. This study highlights the importance of studying local distortion in magnetic materials. This is achieved by combining X-ray absorption spectroscopy with total scattering X-ray diffraction.

Super‐Resolution Imaging in Collagen‐Abundant Thick Tissues

Expansion microscopy (ExM) has gained increasing popularity for 3D ultrastructural imaging of cultured cells and tissue slices at nanoscale resolution using conventional microscopes via physical expansion of biological tissues. However, its application to collagen‐abundant thick tissues is still challenging. Herein, a new method, collagen ExM (ColExM), optimized for expanding tissues containing more than 70% collagen, is demonstrated. ColExM succeeds in 4.5‐fold linear expansion with minimal structural distortion of corneal and skin tissues. It is compatible with immunostaining, allowing super‐resolution visualization of 3D neural structures innervating hair follicles, corneas, and pancreatic tumors with high stromal collagen content. The method succeeds in identifying individual mitochondria and previously unrecognized dendritic spinelike structures of corneal nerves. It also enables fine mapping of structural rearrangement of tight junctions and actin cytoskeletons. Therefore, ColExM can facilitate the exploration of 3D nanoscale structures in collagen‐rich tissues.

Molecular basis of facilitated target search and sequence discrimination of TALE homeodomain transcription factor Meis1

Transcription factors specifically bind to their consensus sequence motifs and regulate transcription efficiency. Transcription factors are also able to non-specifically contact the phosphate backbone of DNA through electrostatic interaction. The homeodomain of Meis1 TALE human transcription factor (Meis1-HD) recognizes its target DNA sequences via two DNA contact regions, the L1-α1 region and the α3 helix (specific binding mode). This study demonstrates that the non-specific binding mode of Meis1-HD is the energetically favored process during DNA binding, achieved by the interaction of the L1-α1 region with the phosphate backbone. An NMR dynamics study suggests that non-specific binding might set up an intermediate structure which can then rapidly and easily find the consensus region on a long section of genomic DNA in a facilitated binding process. Structural analysis using NMR and molecular dynamics shows that key structural distortions in the Meis1-HD–DNA complex are induced by various single nucleotide mutations in the consensus sequence, resulting in decreased DNA binding affinity. Collectively, our results elucidate the detailed molecular mechanism of how Meis1-HD recognizes single nucleotide mutations within its consensus sequence: (i) through the conformational features of the α3 helix; and (ii) by the dynamic features (rigid or flexible) of the L1 loop and the α3 helix. These findings enhance our understanding of how single nucleotide mutations in transcription factor consensus sequences lead to dysfunctional transcription and, ultimately, human disease.

Cr-induced structural phase transformation in sputter deposited poly-AlN thin film from wurtzite to rocksalt structure and their effect on the optical properties

We report Cr doping-induced structural phase transformation (PT) in sputter-deposited polycrystalline-AlN thin film from wurtzite (w) to rocksalt (r) structure. Rietveld analysis shows that the steady substitution of Al ions by Cr ions in the w-AlN lattice distorts and compresses the wurtzite lattice along the c-axis. The chemical pressure exerted in the w-AlN lattice by the compression from the doped Cr ions causes the PT, similar to the high-pressure-induced PT in AlN. Post the PT, the r-Al1-xCrxN thin film continues to exhibit compressive residual stress, indicating that such sustained stress may also play a role in stabilizing the metastable r-Al1-xCrxN phase. The structural distortion and the PT also affected the optical absorption characteristics of the w-Al1-xCrxN thin films. The w-Al1-xCrxN exhibit a direct inter-band transition and the band gap (Eg) decreases from ∼ 6.06 eV for pure w-AlN to ∼ 4.15 eV for w-Al0.73Cr0.27N. After the PT, the r-Al0.61Cr0.39N thin film, on the other hand, exhibits an indirect inter-band transition with an Eg of ∼ 1.84 eV. In addition to the change in Eg, a prominent defect band appears at ∼ 4 eV at low Cr% and another band appears at ∼ 0.98 eV at higher Cr%.

Random field site inequality for ergodicity modification in BNT-based materials: From a phenomenological view

Achieving a simplified BNT-based composition with giant strain properties is challenging, since traditional chemical substitutions rely on trial-and-error experiments and complicates the composition. Herein, we comprehend the strain regulation mechanism from a view of relaxors and propose strain regulation rules based on classical relaxor theory. In BNT-based systems, site inequality of the random field for the ergodicity modification is observed, arising from the discrepant random field-driven (e.g., intensity and action position) structural distortions. From a phenomenological view, B-site substitution is effective in regulating relaxation behaviors due to the stronger lattice softening effect. This work points out the essence of regulating strain properties in BNT-based systems, and the proposed phenomenological relaxation regulation rules are believed to advance the development of actuator applications.