Structural Symmetry Research Articles

Design of pseudosymmetric protein hetero-oligomers

Pseudosymmetric hetero-oligomers with three or more unique subunits with overall structural (but not sequence) symmetry play key roles in biology, and systematic approaches for generating such proteins de novo would provide new routes to controlling cell signaling and designing complex protein materials. However, the de novo design of protein hetero-oligomers with three or more distinct chains with nearly identical structures is a challenging unsolved problem because it requires the accurate design of multiple protein-protein interfaces simultaneously. Here, we describe a divide-and-conquer approach that breaks the multiple-interface design challenge into a set of more tractable symmetric single-interface redesign tasks, followed by structural recombination of the validated homo-oligomers into pseudosymmetric hetero-oligomers. Starting from de novo designed circular homo-oligomers composed of 9 or 24 tandemly repeated units, we redesigned the inter-subunit interfaces to generate 19 new homo-oligomers and structurally recombined them to make 24 new hetero-oligomers, including ABC heterotrimers, A2B2 heterotetramers, and A3B3 and A2B2C2 heterohexamers which assemble with high structural specificity. The symmetric homo-oligomers and pseudosymmetric hetero-oligomers generated for each system have identical or nearly identical backbones, and hence are ideal building blocks for generating and functionalizing larger symmetric and pseudosymmetric assemblies.

Mechanically induced dynamic QBIC-BIC switching and sensing performance enhancement using elastomer-based double resonant gratings

A quasi-bound state in the continuum (QBIC) is a hot topic in optics, as it brings extremely high Q factors by slightly breaking the structural symmetry or tuning geometric parameters. However, QBIC devices are usually not dynamically tunable; thus, achieving this ultra-high Q factor demands ultra-high fabrication accuracy. Here, by first proposing an elastomer-based double resonant gratings (DRG) in the THz band, a strategy to realize dynamically tunable QBIC devices is presented. By simple stretching, structural parameters can be tuned, leading to dynamic QBIC-BIC switching, dynamic Q factors tuning to the order of 106, and enhancement of sensing performance. Moreover, by varying the incident angle, this dynamic tuning is achievable at a constant frequency. The strategy is expected to neutralize the demanding requirements for fabrication accuracy in the implementation of QBIC devices. Hence, it is a promising solution to realize tunable QBIC devices for applications such as THz biosensing.

HybridGNN: A Self-Supervised Graph Neural Network for Efficient Maximum Matching in Bipartite Graphs

Solving maximum matching problems in bipartite graphs is critical in fields such as computational biology and social network analysis. This study introduces HybridGNN, a novel Graph Neural Network model designed to efficiently address complex matching problems at scale. HybridGNN leverages a combination of Graph Attention Networks (GATv2), Graph SAGE (SAGEConv), and Graph Isomorphism Networks (GIN) layers to enhance computational efficiency and model performance. Through extensive ablation experiments, we identify that while the SAGEConv layer demonstrates suboptimal performance in terms of accuracy and F1-score, configurations incorporating GATv2 and GIN layers show significant improvements. Specifically, in six-layer GNN architectures, the combinations of GATv2 and GIN layers with ratios of 4:2 and 5:1 yield superior accuracy and F1-score. Therefore, we name these GNN configurations HybridGNN1 and HybridGNN2. Additionally, techniques such as mixed precision training, gradient accumulation, and Jumping Knowledge networks are integrated to further optimize performance. Evaluations on an email communication dataset reveal that HybridGNNs outperform traditional algorithms such as the Hopcroft–Karp algorithm, the Hungarian algorithm, and the Blossom/Edmonds’ algorithm, particularly for large and complex graphs. These findings highlight HybridGNN’s robust capability to solve maximum matching problems in bipartite graphs, making it a powerful tool for analyzing large-scale and intricate graph data. Furthermore, our study aligns with the goals of the Symmetry and Asymmetry Study in Graph Theory special issue by exploring the role of symmetry in bipartite graph structures. By leveraging GNNs, we address the challenges related to symmetry and asymmetry in graph properties, thereby improving the reliability and fault tolerance of complex networks.

Gradient Luminescence Enhancement in Organic Metal Halide Perovskites via the Suppression of [SbCln]3-n Unit Distortion.

Intrinsic stereochemical activity of the 5s2 electron configuration in Sb3+ leads to structural distortion within [SbCln]3-n units, which, while stabilizing the material, paradoxically diminishes luminescence intensity due to induced asymmetry. To address this issue, a strategy, which encompasses increasing the structural dimensions and introducing In3+ doping, was developed to mitigate the geometrical distortion in the [SbCln]3-n units within the metal-organic perovskite (DABCO)2Sb2Cl10·H2O and (DABCO)2SbCdCl9·2H2O (DABCO = triethylenediamine). This dimensional augmentation confines lattice distortion effectively, and the In3+ doping modifies the 5s2 electron configuration of Sb3+, thereby reducing the distortion at its origin. The unique suitability of indium-based halides as a matrix for Sb3+ doping is underscored by our approach, which capitalizes on their ability to regulate the electron configuration of Sb3+. This strategy has been validated through crystallographic data from single-crystal X-ray diffraction. By effectively reducing the adverse effects of geometric distortion, several hundred-fold enhancements in the luminescent intensity of the material have been achieved by our methodology, leading to potential applications in white-light LEDs. This advancement not only highlights the pivotal role of structural symmetry in the optical properties of materials but also exemplifies the power of material engineering to optimize the optical performance.

Covalent Organic Frameworks for Boosting H2O2 Photosynthesis via the Synergy of Multiple Charge Transfer Channels and Polarized Field

AbstractCovalent organic frameworks (COFs) serve as one of the most promising candidates for hydrogen peroxide (H2O2) photosynthesis, while attaining high‐performance COFs remains a formidable challenge due to the insufficient separation of photogenerated charges. Here, through the rational design of bicarbazole‐based COFs (Cz‐COFs), we showcase the first achievement in piezo‐photocatalytic synthesis of H2O2 using COFs. Noteworthily, the ethenyl group‐modified Cz‐COFs (COF‐DH‐Eth) demonstrates a record‐high yield of H2O2 (9212 μmol g−1 h−1) from air and pure water through piezo‐photocatalysis, which is ca. 2.5 times higher than that of pristine Cz‐COFs without ethenyl groups (COF‐DH‐H) under identical condition and COF‐DH‐Eth without ultrasonic treatment. The H2O2 production rate originates from the synergistic effect between an ultrasonication‐induced polarized electric field and the spatially separated multiple charge transfer channels, which significantly promote the utilization of photogenerated electrons by directional transfer from bicarbazole groups to the ethenyl group‐modified benzene rings. Several Cz‐COFs and bifluorenylidene‐based COFs (COF‐BFTB‐H) with similar twisted monomers exhibit obvious piezoelectric performance for promoting H2O2 generation, signifying that organic ligands with a twistable structure play a crucial role in creating broken symmetry structures, thereby establishing piezoelectric properties in COFs.

Photocontrol of ferroelectricity in multiferroic BiFeO3 via structural modification coupled with photocarrier

Ultrafast control of ferroelectricity and magnetism by light is essential for future development in multiple functioning devices. Here, we demonstrate that the intense and ultrafast photo-modulation of the electric dipole can be realized by photocarrier injection into a multiferroic BiFeO3 thin film using optical pump-probe and second harmonic generation measurements. Results of ultrafast electron diffraction with <100 fs time resolution and theoretical study reveal that the localized photocarrier strongly couples with the lattice structure and becomes the origin for the observed sudden change in the electric dipole. In addition, the subsequent structural dynamics involve a strong oscillation with a frequency of ~3.3 THz despite a poor structural symmetry change. Based on a theoretical calculation, this oscillation can be attributed to an unexpectedly softened new phonon mode generated by mixing essential two phonon modes governing the multiferroic (ferroelectric and antiferromagnetic) nature of BiFeO3 in the ground state due to strong coupling with a localized photocarrier. The comprehensive study shows that injection of the localized photocarrier strongly coupled with the lattice vibration mode can simultaneously realize the ultrafast switching of electric dipoles and magnetic interaction at once, even at room temperature, without modifying the long-range lattice structure.

Anisotropy of the zigzag order in the Kitaev honeycomb magnet α−RuBr3

Kitaev materials often order magnetically at low temperatures due to the presence of non-Kitaev interactions. Torque magnetometry is a very sensitive technique for probing the magnetic anisotropy, which is critical in understanding the magnetic ground state. In this paper, we report detailed single-crystal torque measurements in the proposed Kitaev candidate honeycomb magnet α−RuBr3, which displays zigzag order below 34 K. Based on angular-dependent torque studies in magnetic fields up to 16 T rotated in the plane normal to the honeycomb layers, we find an easy-plane anisotropy with a temperature dependence of the torque amplitude following closely the behavior of the powder magnetic susceptibility. The torque for the field rotated in the honeycomb plane has a clear sixfold periodicity with a sawtooth shape, reflecting the threefold symmetry of the crystal structure and stabilization of different zigzag domains depending on the field orientation, with a torque amplitude that follows an order parameter form inside the zigzag phase. By comparing experimental data with theoretical calculations we highlight the importance of relevant anisotropic interactions and the role of the competition between different zigzag domains in this candidate Kitaev magnet. Published by the American Physical Society 2024

Families of Hamiltonians sharing a common symmetry structure

Families of Hamiltonians sharing a common symmetry structure

Pyramid floating solar still with enhanced condensation surfaces operating under actual weather conditions

The potential solution offered by floating solar still (FSS) to water scarcity confronts challenges associated with condensate droplet loss and structural instability under oceanic and swaying condition. A novel pyramid FSS with reduced wettability surfaces (silicon nano-coated) was proposed, utilizing central symmetry structure of pyramid to reinforce the stability and adopting nano-coated surfaces to enhance the condensation. A 4-day outdoor experiment was conducted to evaluate the performance. The highest yield of nano-coated FSS was 1.017 kg/m2/d under an accumulated irradiation of 15.166 MJ/m2/d, which was 16.76% higher than that of uncoated FSS. Furthermore, the yield of nano-coated FSS was 0.949 kg/m2/d in the river experiment, showing a significant improvement. Next, the enhancement of nano-coated surface on droplet collection was numerically analyzed, showing that the condensation droplets could retain their complete shape until detachment. In contrast, the detachment process on the uncoated surface involved a separation of neck, leaving a residue of liquid behind. Quantitative analysis showed longer movement distances and faster travel velocities for droplets on the nano-coated surface, and these two improvements could facilitate condensate collection. Furthermore, the cost analysis reveals a CPL of 0.129 $/L for the proposed FSS, suggesting its affordability for off-grid communities.

Eu3+-doped bismuth silicate crystal structure and Mulliken charge analysis.

The effects of Eu3+ doping on the crystal structure and charge distribution of Bi4Si3O12 (BSO) bisilicate, based on first principles and density functional theory (DFT), were calculated and analyzed using Materials Studio software. The effect of different proportions (1/12, 1/6 and 1/3) of Eu3+ doping on BSO crystals was investigated using the virtual crystal approximation method. Through Mulliken charge analysis, it is found that a high proportion of Eu3+ doping will destroy the symmetry of the crystal structure. With an increase of the Eu3+-doping ratio, the Eu-O bond length first increased and then decreased, showing the characteristics of covalent bonds, and the Eu-O bond length reached the minimum value when the Eu3+-doping ratio was increased to 1/3. With an increase in the Eu3+-doping ratio, the Bi-O bond length decreases sequentially and also reaches the minimum value when the Eu3+-doping ratio was increased to 1/3. This indicates that the covalence between the Eu-O and Bi-O atoms is enhanced when the doping ratio is 1/3 when BSO crystals are doped with Eu3+.

Covalent Organic Frameworks for Boosting H2O2 Photosynthesis via the Synergy of Multiple Charge Transfer Channels and Polarized Field.

Covalent organic frameworks (COFs) serve as one of the most promising candidates for hydrogen peroxide (H2O2) photosynthesis, while attaining high-performance COFs remains a formidable challenge due to the insufficient separation of photogenerated charges. Here, through the rational design of bicarbazole-based COFs (Cz-COFs), we showcase the first achievement in piezo-photocatalytic synthesis of H2O2 using COFs. Noteworthily, the ethenyl group-modified Cz-COFs (COF-DH-Eth) demonstrates a record-high yield of H2O2 (9212 μmol g-1 h-1) from air and pure water through piezo-photocatalysis, which is ca. 2.5 times higher than that of pristine Cz-COFs without ethenyl groups (COF-DH-H) under identical condition and COF-DH-Eth without ultrasonic treatment. The H2O2 production rate originates from the synergistic effect between an ultrasonication-induced polarized electric field and the spatially separated multiple charge transfer channels, which significantly promote the utilization of photogenerated electrons by directional transfer from bicarbazole groups to the ethenyl group-modified benzene rings. Several Cz-COFs and bifluorenylidene-based COFs (COF-BFTB-H) with similar twisted monomers exhibit obvious piezoelectric performance for promoting H2O2 generation, signifying that organic ligands with a twistable structure play a crucial role in creating broken symmetry structures, thereby establishing piezoelectric properties in COFs.

Observation of interface-induced nonlocal spin-torques from Gd/Pt interface

We investigate spin–orbit torques (SOTs) generated by Gd/Pt and Ti/Pt interfaces by performing spin-torque ferromagnetic resonance measurements at room temperature. We report a sizable spin-current created by the Gd/Pt interface, exhibiting the damping-like-torque efficiency per unit electric field, ξDLE=−8 ± 0.6×104ℏ2e(Ωm)−1 as observed in Gd(5 nm)/Pt(1.5 nm)/Py(3 nm-6 nm)/Pt(1.5 nm) heterostructures. This interface-induced spin-current is attributed to the vertical electric field produced by the broken structural inversion symmetry, with a work function difference of 2.75 eV between Gd and Pt. This is further substantiated by varying the thickness of the Gd-layer. We compare these results with the Ti/Pt interface, which has a work function difference of 1.3 eV, by implementing Ti(5 nm)/Pt(1.5 nm)/Py(3 nm-6 nm)/Pt(1.5 nm) heterostructures. We find that the spin-current induced by the Ti/Pt interface is too small to overcome the remnant SOTs caused by the asymmetrically grown Pt layers on both sides of Py. Our work reveals the role of interface-induced spin currents for practical applications, which can be leveraged to produce robust spin torques that complement the bulk spin-Hall torque.

Vector Reconfiguration on a Bidirectional Multilevel LCL-T Resonant Converter

With the development of distributed energy technology, the establishment of the energy internet has become a general trend, and relevant research about the core component, energy router, has also become a hotspot. Therefore, the bidirectional isolated DC–DC converter (BIDC) is widely used in AC–DC–AC energy router systems, because it can flexibly support the DC bus voltage ratio and achieve bidirectional power flow. This paper proposes a novel vector reconfiguration on a bidirectional multilevel LCL-T resonant converter in which an NPC (neutral-point clamped) multilevel structure with a flying capacitor is introduced to form a novel active bridge, and a coupling transformer is specially added into the active bridge to achieve multilevel voltage output under hybrid modulation. In addition, an LCL-T two-port vector analysis is adopted to elaborate bidirectional power flow which can generate some reactive power to realize zero-voltage switching (ZVS) on active bridges to improve the efficiency of the converter. Meanwhile, due to the symmetry of the LCL-T structure, the difficulty of the bidirectional operation analysis of the power flow is reduced. Finally, a simulation study is designed with a rated voltage of 200 V on front and rear input sources which has a rated power of 450 W with an operational efficiency of 93.8%. Then, the feasibility of the proposed converter is verified.

Influence of polymorphism on the lattice thermal conductivity of Ga2O3

In this paper, the lattice thermal conductivity of Ga2O3 in its β, α, ɛ(κ), and γ phase is systematically investigated based on the first principles calculation and iterative approaches to solve the phonon Boltzmann equation. The results indicate that the crystal microstructure of Ga2O3 has a significant effect on the lattice thermal conductivity. In addition, the results also find that γ-Ga2O3 has an ultralow lattice thermal conductivity within the temperature range from 50 to 700 K. As for γ-Ga2O3, the obtained lattice thermal conductivity at room temperature (300 K) is 0.1189 W/(m K) along the [100] and [010] directions, and 0.1159 W/(m K) along the [001] direction. The lattice thermal conductivity exhibits the following order: γ-Ga2O3 ≪ ɛ(κ)-Ga2O3 &amp;lt; α-Ga2O3 &amp;lt; β-Ga2O3. The disruptive effect of Ga3+ cation vacancies on the spinel structure's symmetry is responsible for the ultralow lattice thermal conductivity observed in γ-Ga2O3. This disruption increases the complexity of the lattice and hampers the propagation and scattering of phonons. Another contributing factor is the presence of weak chemical bonding, which intensifies the oscillation of Ga atoms. The results of this study have significant implications for further investigating the factors influencing the thermal conductivity of Ga2O3 and developing thermoelectric materials.

Theoretical Study on Singlet Fission Dynamics and Triplet Migration Process in Symmetric Heterotrimer Models.

Singlet fission (SF) is a photophysical process where one singlet exciton splits into two triplet excitons. To construct design guidelines for engineering directional triplet exciton migration, we investigated the SF dynamics in symmetric linear heterotrimer systems consisting of different unsubstituted or 6,13-disubstituted pentacene derivatives denoted as X/Y (X, Y: terminal and center monomer species). Time-dependent density functional theory (TDDFT) calculations clarified that the induction effects of the substituents, represented as Hammett's para-substitution coefficients σp, correlated with both the excitation energies of S1 and T1 states, in addition to the energies of the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO). Electronic coupling calculations and quantum dynamics simulations revealed that the selectivity of spatially separated TT states for heterotrimers increased over 70%, superior to that in the homotrimer: an optimal region of the difference in σp between the substituents of X and Y for the increase in SF rate was found. The origin of the rise in SF rate is explained by considering the quantum interference effect: reduction in structural symmetry opens new interaction paths, allowing the S1-TT mixing, which contributes to accelerating the hetero-fission between the terminal and center molecules.

Rebuilding Peripheral F, Cl, Br Footprints on Acceptors Enables Binary Organic Photovoltaic Efficiency Exceeding 19.7 %

AbstractGiven homomorphic fluorine (F), chlorine (Cl) and bromine (Br) atoms are featured with gradually enlarged polarizability/atomic radius but decreased electronegativity, the rational screen of halogen species and locations on small molecular acceptors (SMAs) is quite essential for acquiring desirable molecular packing to boost efficiency of organic solar cells (OSCs). Herein, three isomeric SMAs (CH−F, CH−C and CH−B) are constructed by delicately rebuilding peripheral F, Cl, Br footprints on both central and end units. Such a re‐permutation of peripheral halogens could not only maintain the structural symmetry of SMAs to the maximum, but also acquire extra asymmetric benefits of enhanced dipole moment and intramolecular charge transfer, etc. Moreover, central brominating enhances molecular crystallinity of CH−B without introducing undesirable steric hindrance on end groups, thus rendering a better balance between high crystallization and domain size control in PM6:CH−B blend. Further benefitting from the large dielectric constant, small exciton binding energy, optimized molecular packing and great electron transfer integral, CH−B affords the first class binary OSC efficiency of 19.78 %, moreover, the highest efficiency of 18.35 % thus far when increasing active layer thickness to ~300 nm. Our successful screening in rebuilding peripheral halogen footprints provides the valuable insight into further rational design of SMAs for record‐breaking OSCs.

Three-channel demultiplexer based on one-dimensional magnonic crystal waveguides using defect modes

Abstract In this work, the transfer matrix method is used to study magnetostatic spin waves (SWs) in magnonic crystal (MC) waveguide. By eliminating structural symmetry and creating a defect in a completely periodic structure, the localization of SWs with frequencies corresponding to the defect mode in the band gap has been realized. The proposed structure consists of three yttrium-iron-garnet films with the same thickness, 5 μm, with an array of etched grooves with different defects. The designed demultiplexer filters specific frequencies with high precision and directs them to designated outputs. The quality factor for the MC waveguides is 20901, 20903 and 20904 at central frequency of 6.2704 GHz, 6.2709 GHz and 6.2714 GHz, respectively. The results demonstrate that the proposed structure leads to the realization of the three-channel GHz-ranged demultiplexer in magnonic circuits.

Effect of rare earth doping on structural, morphological, optical, and magnetic properties of the Y1-x(Gd, Dy)xBaCuFeO5 (x = 0.2, 0.4, 0.6, and 0.8) ceramics

The effect of the rare earth (RE) ion substitution on the structural, morphological, optical and magnetic properties of the Y1-xRExBaCuFeO5 (RE = Gd, Dy; x = 0.2, 0.4, 0.6, and 0.8) multiferroic compounds grown by the solid-state reaction is evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), dispersive X-ray spectroscopy (EDX), reflectance spectroscopy techniques diffuse (UV–vis–NIR) and vibrating sample magnetometry (VSM). The results indicate that the RE substitution led to growth of single-phase materials, with a tetragonal structure and P4mm symmetry. The morphological analysis shows the formation of polycrystalline materials composed of grains of various shapes and sizes. Furthermore, the compositional analysis reveals that the materials do not present elements other than those used in the synthesis. The band gap (Eg) is tuned from 0.88 to 0.90 eV upon RE substitution. The magnetization curves obtained in the Zero-Field-Cooled/Field-Cooled (ZFC-FC) modes between 50 and 390 K, reveal a paramagnetic behavior, which could be attributed to the dominance exerted by the magnetic moments of the Gd/Dy ions.

Rebuilding Peripheral F, Cl, Br Footprints on Acceptors Enables Binary Organic Photovoltaic Efficiency Exceeding 19.7 .

Given homomorphic fluorine (F), chlorine (Cl) and bromine (Br) atoms are featured with gradually enlarged polarizability/atomic radius but decreased electronegativity, the rational screen of halogen species and locations on small molecular acceptors (SMAs) is quite essential for acquiring desirable molecular packing to boost efficiency of organic solar cells (OSCs). Herein, three isomeric SMAs (CH-F, CH-C and CH-B) are constructed by delicately rebuilding peripheral F, Cl, Br footprints on both central and end units. Such a re-permutation of peripheral halogens could not only maintain the structural symmetry of SMAs to the maximum, but also acquire extra asymmetric benefits of enhanced dipole moment and intramolecular charge transfer, etc. Moreover, central brominating enhances molecular crystallinity of CH-B without introducing undesirable steric hindrance on end groups, thus rendering a better balance between high crystallization and domain size control in PM6:CH-B blend. Further benefitting from the large dielectric constant, small exciton binding energy, optimized molecular packing and great electron transfer integral, CH-B affords the first class binary OSC efficiency of 19.78 %, moreover, the highest efficiency of 18.35 % thus far when increasing active layer thickness to ~300 nm. Our successful screening in rebuilding peripheral halogen footprints provides the valuable insight into further rational design of SMAs for record-breaking OSCs.

Multi-scenario refractive index sensor based on merging BIC in an all-dielectric metasurface

In recent years, bound states in the continuum (BICs) in the all-dielectric metasurfaces have attracted considerable attention due to the low radiation loss and large quality factor (Q-factor). In this study, we design a highly sensitive refractive index sensor working in multi-scenario based on merging quasi-BIC in the silicon nitride metasurface. By adjusting the thickness of the metasurface and keeping the structural symmetry, nine BICs distributed in momentum space form the merging BIC at the Γ point with significantly enhanced Q-factor. The transmission spectra of the metasurface sensor disperse with the refractive index in multi-scenario. The modulation depth of the Fano resonance spectrum can exceed 99.9%. The sensitivity and figure of merit of the refractive index sensor based on the merging quasi-BIC can reach 41.35 nm/RIU and 13,389.1 RIU-1 for gas, 59.05 nm/RIU and 8,415.9 RIU-1 for blood, and 66.08 nm/RIU and 8,845.8 RIU-1 for cerebrospinal fluid, respectively. Furthermore, we investigate the influence of the structural deviations on the Q-factor, which of the merging quasi-BIC maintains higher than that of the isolated quasi-BIC. Our work offers a method for designing high-sensitivity sensors working in multi-scenarios, which may hold significant potential for enhancing device performance in gas and biological detection.