Crystallographic Symmetry Research Articles

Full‐Color Luminescence from Single‐Component Hydrocarbon Crystal: RGB Emission by Altering Molecular Packing Under Pressure

AbstractFull‐color emission from solid single‐component organic materials is highly desired to realize inexpensive and non‐toxic organic electronics. However, as the three primary colors, red, green, and blue (RGB), have significantly different energies, observation of RGB luminescence from a single‐component molecule is extremely challenging. In this study, a coronene nanorod single‐component single‐crystal is prepared, which exhibits blue fluorescence at ambient conditions and realizes full‐color emission, for the first time, by altering the molecular packing through high‐pressure compression. A valuable insight into the relationships between structure and optical properties of coronene at high pressures is obtained by combining various spectroscopic studies. During compression, it is found that the tuneable piezochromic luminescence of coronene is strictly related to the molecular packing and crystallographic symmetry. This study not only provides insight into the structure‐optical property relationships of hydrocarbon but also promotes the development of single molecular systems with different molecular packing that exhibit RGB emissions even at ambient conditions even with a single excitation wavelength.

Solid-State Electrochemistry on Supramolecular Assemblies with Strong Isotropic Property

It has been mathematically proven that only honeycomb, diamond, and K4 lattices have a special symmetry called "strong isotropy". Note that crystallographic symmetry is determined only by the position of atoms, while strong isotropy is governed by both the position of atoms and bonds. The K4 lattice, called by various names such as gyroid lattice and srs network, is characterized by the fact that it exhibits chirality. It is recognized that their mathematically-defined “line graphs” correspond to kagome, hyper-kagome, and pyrochlore lattices, respectively, which are well known as spin frustration lattices. This relation suggests that the materials with the strong isotropic lattices possess “hidden” frustration. It is also noteworthy that the band structure of the three lattices contains exotic band dispersions such as Dirac cones due to their lattice symmetry, and that they possess porous structures. From this perspective, we proposed to form the supramolecular assemblies with the with strong isotropic property, and to carry out electrochemical valence control for realizing exotic physical properties such as Dirac electron, spin frustration, etc.In this presentation, we will explain our previous works on the solid-state electrochemistry of LiPc as an introduction. Then, we will report the rational synthesis of the molecule-based honeycomb and K4 structures, using MOF/COF- and supramolecular-chemistry, the nanohybridization using their porous structures, the physical properties such as spin frustration and circularly polarized luminescence, and the solid-state electrochemical redox control on them without destroying the original frameworks.

Local displacive correlation in the tetragonal relaxor ferroelectric Pb(Zn1/3Nb2/3)O3-0.15PbTiO3

Over the past decades, lead-based relaxor ferroelectrics have served as the model systems to unravel the relationship between electromechanical properties and local structure. Here, by employing pair distribution function analysis and the reverse Monte Carlo method, we investigate the local structural features and their temperature dependence in relaxor ferroelectric Pb(Zn1/3Nb2/3)O3-xPbTiO3 with x = 0.15 (PZN-15PT), which has a tetragonal average structure, but displays frequency dependence at low temperatures. The refined atomic model suggests that ordered polar nanoregions (PNRs) originate from the strong atomic displacive correlation, and their polar directions are the same as the crystallographic symmetry axis. The dipoles in the disordered matrix have weak correlations and can be averaged into a global tetragonal symmetry. These findings establish a detailed picture of the local structure of lead-based relaxor ferroelectrics and provide a deeper insight into the nature of PNRs.

New Crystal Form of Human Neuropilin-1 b1 Fragment with Six Electrostatic Mutations Complexed with KDKPPR Peptide Ligand.

Neuropilin 1 (NRP1), a cell-surface co-receptor of a number of growth factors and other signaling molecules, has long been the focus of attention due to its association with the development and the progression of several types of cancer. For example, the KDKPPR peptide has recently been combined with a photosensitizer and a contrast agent to bind NRP1 for the detection and treatment by photodynamic therapy of glioblastoma, an aggressive brain cancer. The main therapeutic target is a pocket of the fragment b1 of NRP1 (NRP1-b1), in which vascular endothelial growth factors (VEGFs) bind. In the crystal packing of native human NRP1-b1, the VEGF-binding site is obstructed by a crystallographic symmetry neighbor protein, which prevents the binding of ligands. Six charged amino acids located at the protein surface were mutated to allow the protein to form a new crystal packing. The structure of the mutated fragment b1 complexed with the KDKPPR peptide was determined by X-ray crystallography. The variant crystallized in a new crystal form with the VEGF-binding cleft exposed to the solvent and, as expected, filled by the C-terminal moiety of the peptide. The atomic interactions were analyzed using new approaches based on a multipolar electron density model. Among other things, these methods indicated the role played by Asp320 and Glu348 in the electrostatic steering of the ligand in its binding site. Molecular dynamics simulations were carried out to further analyze the peptide binding and motion of the wild-type and mutant proteins. The simulations revealed that specific loops interacting with the peptide exhibited mobility in both the unbound and bound forms.

A Highly Active and Reusable Multicomponent high Entropy Metal Oxide Catalyst for Nitroarenes Hydrogenation

It is well known that multicomponent catalysts can improve catalytic performance, however their rational design and precise control of catalytic activities by varying the composition of the elements is challenging. Herein, we present a facile and scalable synthetic strategy for production of senary and septenary metal oxide nanoparticles with a chemical composition of MSbOx and MSb2Ox (M: Fe, Ni, Co, Cu, and Zn). All samples were formed in a tetragonal crystal structure with space group 136 and crystallographic symmetry P42/mnm while the details of their constituent unit cells are different, belonging to rutile or trirutile structures. These nanocomposites have an oxygen vacancy-rich construction with uniform elemental distributions that produce various surface functionalities. They showed instantaneous hydrogenation catalytic performance for reduction of 4-nitrophenol to 4-aminophenol at room temperature. Among our samples, the senary catalyst with MSbOx chemical composition showed better durability and reusability owning to its morphological and microstructural properties. It showed 100% conversion of 4-nitrophenol to 4-aminophenol within 4 min at the 18th run without any by-products.

1-[1,4-Bis(but-3-en-1-yl-oxy)]-2,3,4,5-(1,4-dimeth-oxy)pillar[5]arene-1,4-di-bromo-butane 1:1 inclusion complex.

In the title compound, C51H58O10·C4H8Br2, both the host and guest are completed by crystallographic twofold symmetry (one carbon atom of the host lies on the rotation axis). The penta-gonal-shaped macrocycle has a pair of butene-oxy substituents on one of its faces and one mol-ecule of 1,4-di-bromo-butane is encapsulated within the cavity of the pillararene, forming a 1:1 inclusion complex. The terminal alkene parts, which project outwards from the pillararene ring, exhibit positional disorder over two sets of sites in a 0.52 (2): 0.48 (2) ratio. The host and guest inter-act via C-H⋯O, C-H⋯Br and C-H⋯π inter-actions and adjacent host mol-ecules inter-act via C-H⋯O and C-H⋯π bonds.

Direct photoluminescence manipulation in Er-doped AgNbO3 lead-free antiferroelectrics via reversible electric-field-induced symmetry modulations

The electric field-modulated photoluminescent (E-PL) effect has received much attention because of its potential applications in optical data storage and communication. Based on the E-induced antiferroelectric-ferroelectric (AFE-FE) phase transition, a large and reversible modulation of the PL intensity was previously realized in lanthanum-doped Pb(Zr0.9Ti0.1)O3 (PLZT) ceramics. However, such systems contain abundant leads and are thus toxic to humans and the environment. In this work, Er-doped AgNbO3 (ANO) lead-free ceramics were prepared, and their E-PL effect was investigated. From the perspective of the crystallographic symmetry, the reversibly E-induced orthorhombic Pbcm to orthorhombic Pmc21 transition results in a negative PL intensity change of 25%, which is different from the positive 30% PL modulation in the PLZT system triggered by the AFE-FE orthorhombic-rhombohedral phase transition. This symmetry-dependent negative PL modulation in ANO ceramics enriches the understanding of the E-PL effect in AFEs and provides an environmentally friendly alternative for multifunctional optoelectronics.

A Remarkably Unsymmetric Hexairon Core Embraced by Two High-Symmetry Tripodal Oligo-α-pyridylamido Ligands.

Oligo-α-pyridylamides offer an appealing route to polyiron complexes with short Fe-Fe separations and large room-temperature magnetic moments. A derivative of tris(2-aminoethyl)amine (H6tren) containing three oligo-α-pyridylamine branches and 13 nitrogen donors (H6L) reacts with [Fe2(Mes)4] to yield an organic nanocage built up by two tripodal ligands with interdigitated branches (HMes = mesitylene). The nanocage has crystallographic D3 symmetry but hosts a remarkably unsymmetric hexairon-oxo core, with a central Fe5(μ5-O) square pyramid, two oxygen donors bridging basal sites, and an additional Fe center residing in one of the two tren-like pockets. Bond valence sum (BVS) analysis, density functional theory (DFT) calculations, and electrochemical data were then used to establish the protonation state of oxygen atoms and the formal oxidation states of the metals. For this purpose, a specialized set of BVS parameters was devised for Fe2+-N3- bonds with nitrogen donors of oligo-α-pyridylamides. This allowed us to formulate the compound as [Fe6O2(OH)(H3L)L], with nominally four FeII ions and two FeIII ions. Mössbauer spectra indicate that the compound contains two unique FeII sites, identified as a pair of closely spaced hydroxo-bridged metal ions in the central Fe5(μ5-O) pyramid, and a substantially valence-delocalized FeII2FeIII2 unit. Broken-symmetry DFT calculations predict strong ferromagnetic coupling between the two iron(II) ions, leading to a local S = 4 state that persists to room temperature and explaining the large magnetic moment measured at 300 K. The compound behaves as a single-molecule magnet, with magnetization dynamics detectable in zero static field and dominated by an Orbach-like mechanism with activation parameters Ueff/kB = 49(2) K and τ0 = 4(2) × 10-10 s.

Machine learning prediction of thermal and elastic properties of double half-Heusler alloys

Double half-Heusler alloys are promising materials for applications as magnetocaloric materials, topological insulators, but especially thermoelectric materials. Four different elements in their composition provide a wide range of possible compositions, which, on the other hand, is difficult to study directly by applying traditional first-principles approaches to large number of compositions. In this work, based on the gradient boosting method, regression models are constructed that allow rapid prediction of the lattice thermal conductivity, as well as a number of other thermal and elastic properties, based on the composition and crystal structure of a compound. This made it possible for the first time to calculate the lattice thermal conductivity, as well as Grüneisen parameter, Debye temperature, and elastic moduli for a number of double half-Heusler compounds. We observe that the predicted thermal conductivity is in better agreement with the experimental data than the results of density functional theory calculations available in the literature. Half-Heusler compounds with thermal conductivity values lower than those previously known have been found. In addition, we have analyzed the importance of various features for predicting each of the studied properties, and the effect of the crystallographic symmetry of the compound on the prediction accuracy.

GROUPOID OF INTERMOLECULAR CONTACTS AND ITS FUZZY CAYLEY GRAPH

The article defi nes a group of intermolecular contacts for a monosystemic molecular structure described by one of the crystallographic symmetry groups (space, subperiodic, point) in n-dimensional Euclidean space with unoccupied special positions. The defi nition of a monoid of contacts for a polysystemic molecular structure is given. Crisp and fuzzy Cayley graphs of groups and monoids of contacts are constructed. Some examples of crystal structures are considered.

Multi-symmetry high-entropy relaxor ferroelectric with giant capacitive energy storage

Relaxor ferroelectric ceramics with remarkable energy storage performance, which is dominantly determined by polarization and breakdown strength, are one of the bottlenecks for next generation high/pulsed power dielectric capacitors. Herein, we report that high-entropy composition Li2CO3-densified Bi0.2Na0.2Ba0.2Sr0.2Ca0.2TiO3 achieves a giant recoverable energy density (Wrec) of 10.7 J/cm3 and an ultrahigh efficiency (η) of 89 %. To understand the mechanism, the influence of the high-entropy effect on atomic-scale polarization configuration and macroscale electrical properties has been investigated systematically. Randomly distributed A-site ions and B-site ions form complex interactions, which lead to coexisted atomic-scale low crystallographic symmetries, and thus, high-dynamic polar nanoregions as well as “intermediate polarization”, such multiple symmetry polarization configuration ensures fast and strong polarization response. On the other hand, the high-entropy system exhibits a wide band gap, helping to reduce conductivity and delay breakdown. Moreover, stable high-entropy structure brings great advantages for enhancing the thermal/frequency stability of energy storage performance. This work not only provides a material candidate with outstanding comprehensive energy storage performance but also affirms high-entropy approach is a shortcut to optimizing functional property by multi-scale interactions between polarization, microstructure and crystal structure.

Symmetry‐Enforced 2D Hourglass Phononic Nodal Net

Topological nodal‐line semimetals have received extensive attention in recent years, and they exhibit a variety of shapes under various crystallographic symmetry protections, including nodal rings, nodal chains, and nodal knots. By using symmetry analysis and an effective force constant model, it is proposed that a class of 2D hourglass nodal nets protected by nonsymmorphic symmetry can exist in the space group , where the glide operations play a crucial role in the formation of the nets. Further effective model analysis shows that the connect points of the nets are Dirac points that are forced by the symmetries. Based on first‐principle calculations, it is predicted that this nodal net can be realized in the phonon dispersion of 3D Sn. The Berry phase and nontrivial surface states further support its nontrivial topological characteristics. Herein, the studies expand the nodal structure in the study of nodal line in phononic systems and offer a solid foundation for subsequent experimental investigation on this challenging topological state.

Theoretical and numerical modeling of Rayleigh wave scattering by an elastic inclusion

This work presents theoretical and numerical models for the backscattering of two-dimensional Rayleigh waves by an elastic inclusion, with the host material being isotropic and the inclusion having an arbitrary shape and crystallographic symmetry. The theoretical model is developed based on the reciprocity theorem using the far-field Green's function and the Born approximation, assuming a small acoustic impedance difference between the host and inclusion materials. The numerical finite element (FE) model is established to deliver a relatively accurate simulation of the scattering problem and to evaluate the approximations of the theoretical model. Quantitative agreement is observed between the theoretical model and the FE results for arbitrarily shaped surface/subsurface inclusions with isotropic/anisotropic properties. The agreement is excellent when the wavelength of the Rayleigh wave is larger than, or comparable to, the size of the inclusion, but it deteriorates as the wavelength gets smaller. Also, the agreement decreases with the anisotropy index for inclusions of anisotropic symmetry. The results lay the foundation for using Rayleigh waves for quantitative characterization of surface/subsurface inclusions, while also demonstrating its limitations.

Twinned dendrites growth in wire arc directed energy deposition of Al-Zn-Mg-Cu alloy

Twinned dendrites have attracted worldwide attention in the past half century due to their unusual orientation and crystallographic symmetry. Successive research has established a basic understanding of them in relatively steady processes like direct chill casting and directional solidification. This work, for the first time, investigated the growth behaviors of twinned dendrites in the wire arc directed energy deposition. The crystallographic characteristics, formation, and evolution laws of the twinned dendrites in the unsteady localized solidification condition are explored via experiments and numerical simulations. Results show that stacking faults are vital in the longitudinal growth of twinned dendrites by adjusting intermittent twin boundaries. During deposition, Mg, Zn, and Cu, which have low stacking fault energy, can promote the growth of twinned dendrites. The molten pool tail has large temperature gradients, crystallization velocities, and sufficient convection, providing advantageous growth conditions for twinned dendrites. Competitive relationships form between twinned and regular dendrites at the molten pool center. However, the twinned dendrites also cooperate with regular dendrites in epitaxial growth via their 〈100〉 lateral branch. With the remelting depth increasing, the twinned dendrite morphology changes from lamellar to isolated unilateral feather shape, then to unchained islands, and finally disappear.

Syntheses, Characterization, Crystal Structures and Antimicrobial Activity of Copper(II), Nickel(II) and Zinc(II) Complexes Derived from 5-Bromo-2- ((cychlopentylimino)methyl)phenol

Four new complexes of copper(II), nickel(II) and zinc(II), [CuL2] (1), [Ni3L2(4-BrSal)2(CH3COO)2(CH3OH)2]·2CH3OH (2), [ZnBr2(HL)2] (3) and [ZnL(dca)]n (4), where L is 5-bromo-2-(cychlopentylimino)methyl)phenolate, HL is the zwitterionic form of 5-bromo-2-((cychlopentylimino)methyl)phenol, 4-BrSal is the monoanionic form of 4-bromosalicylaldehyde, dca is dicyanamide anion, were synthesized and characterized by elemental analysis, IR and UV-Vis spectroscopy. The structures of the complexes were further confirmed by single crystal X-ray structure determination. Complex 1 is a mononuclear copper(II) compound, with a crystallographic two-fold rotation axis symmetry. The Cu atom is in distorted square planar coordination. Complex 2 is a trinuclear nickel(II) compound, with an inversion center symmetry. The Ni atoms are in octahedral coordination. Complex 3 is a mononuclear zinc(II) compound, while complex 4 is a dca bridged polymeric zinc(II) compound. The Zn atoms are in tetrahedral coordination. The compounds were assayed for their antimicrobial activities.

Syntheses, Characterization, Crystal Structures and Antimicrobial Activity of Copper(II), Nickel(II) and Zinc(II) Complexes Derived from 5-Bromo-2-((cychlopentylimino)methyl)phenol.

Four new complexes of copper(II), nickel(II) and zinc(II), [CuL2] (1), [Ni3L2(4-BrSal)2(CH3COO)2(CH3OH)2]·2CH3OH (2), [ZnBr2(HL)2] (3) and [ZnL(dca)]n (4), where L is 5-bromo-2-((cychlopentylimino)methyl)phenolate, HL is the zwitterionic form of 5-bromo-2-((cychlopentylimino)methyl)phenol, 4-BrSal is the monoanionic form of 4-bromosalicylaldehyde, dca is dicyanamide anion, were synthesized and characterized by elemental analysis, IR and UV-Vis spectroscopy. The structures of the complexes were further confirmed by single crystal X-ray structure determination. Complex 1 is a mononuclear copper(II) compound, with a crystallographic two-fold rotation axis symmetry. The Cu atom is in distorted square planar coordination. Complex 2 is a trinuclear nickel(II) compound, with an inversion center symmetry. The Ni atoms are in octahedral coordination. Complex 3 is a mononuclear zinc(II) compound, while complex 4 is a dca bridged polymeric zinc(II) compound. The Zn atoms are in tetrahedral coordination. The compounds were assayed for their antimicrobial activities.

Transformation from Magnetic Soliton to Skyrmion in a Monoaxial Chiral Magnet.

Topological spin textures are of great interest for both fundamental physics and applications in spintronics. The Dzyaloshinskii-Moriya interaction underpins the formation of single-twisted magnetic solitons or multi-twisted magnetic skyrmions in magnetic materials with different crystallographic symmetries. However, topological transitions between these two kinds of topological objects have not been verified experimentally. Here, the direct observation of transformations from a chiral soliton lattice (CSL) to magnetic skyrmions in a nanostripe of the monoaxial chiral magnet CrNb3 S6 using Lorentz transmission electron microscopy is reported. In the presence of an external magnetic field, helical spin structures first transform into CSLs and then evolve into isolated elongated magnetic skyrmions. The detailed spin textures of the elongated magnetic skyrmions are resolved using off-axis electron holography and are shown to comprise two merons, which enclose their ends and have unit total topological charge. Magnetic dipolar interactions are shown to play a key role in the magnetic soliton-skyrmion transformation, which depends sensitively on nanostripe width. The findings here, which are consistent with micromagnetic simulations, enrich the family of topological magnetic states and their transitions and promise to further stimulate the exploration of their emergent electromagnetic properties.

Crystal structure, Hirshfeld surface analysis and DFT study of (5E,5'E,6Z,6'Z)-6,6'-[ethane-1,2-diyl-bis(aza-nylyl-idene)]bis-{5-[2-(4-fluoro-phen-yl)hydra-zono]-3,3-di-methyl-cyclo-hexa-none} 2.5-hydrate.

The title compound, C30H34F2N6O2·2.5H2O, was obtained by condensation of 2-[2-(4-fluoro-phen-yl)hydrazono]-5,5-di-methyl-cyclo-hexan-1,3-dione with ethyl-enedi-amine in ethanol and crystallized as a 1:2.5 hydrate in space group C2/c. The two independent mol-ecules, with approximate crystallographic C 2 symmetries, have different conformations and packing environments, are stabilized by intra-molecular N-H⋯N hydrogen bonds and linked by O-H⋯O hydrogen bonds involving the water mol-ecules. A Hirshfeld surface analysis showed that H⋯H contacts make by far the largest (48-50%) contribution to the crystal packing. From DFT calculations, the LUMO-HOMO energy gap of the mol-ecule is 0.827 eV.

Self-Assembling Systems for Optical Out-of-Plane Coupling Devices.

Micromirrors are used in integrated photonics to couple extraplanar light into the planar structure of a device by redirecting light via specular reflection. Compared with grating or prism-based couplers, micromirrors allow for coupling of light over a broader range of wavelengths, provided that the micromirror is fabricated with a specific 3D shape to ensure proper reflection angles. In principle, self-assembly methods could enable reliable, parallelizable fabrication of such devices with a high degree of precision by designing self-assembling components that produce the desired microscale geometry as their thermodynamic products. In this work, we use DNA-functionalized nanoparticles to assemble faceted crystallites with predetermined crystal shapes, and demonstrate with microscale retroreflectance measurements that these self-assembled nanoparticle arrays do indeed behave like optically flat mirrors. Furthermore, we show that the tilt angle of the micromirrors can be intentionally controlled by altering the crystallographic symmetry and preferred crystal orientations as a function of the self-assembly process, thereby altering the resulting specular angle in a programmable manner. Measurements of optical coupling from normal incidence into the substrate plane via an optical fiber confirm that the faceted structures can function as optical out-of-plane coupling devices, and coating these structures with reflective materials allows for high efficiency of light reflection in addition to the angular control. Together, these experiments demonstrate how self-assembled nanoparticle materials can be used to generate optically relevant architectures, enabling a significant step in the development of self-assembly as a materials fabrication tool for integrated optical devices.

Real-Space Observation of Ripple-Induced Symmetry Crossover in Ultrathin MnPS3.

Stacking order is expected to have a significant impact on the properties of van der Waals layered magnets, as it determines the crystallographic and magnetic symmetry. Recent synchrotron-based optical studies on antiferromagnetic MnPS3 have revealed a thickness-dependent symmetry crossover, suggesting possible different stackings in few-layer crystals from the bulk, which, however, has not been explicitly identified. Here, by using a combination of atomic-scale electron microscopy and theoretical calculations, we show that despite the bulk monoclinic stacking persists macroscopically down to bilayer, additional local rippling effect lifts the monoclinic symmetry of the few layers while preserving the trigonal symmetry of individual monolayers, leading to possible monolayer-like behavior in ultrathin MnPS3 samples. This finding reveals the profound impact of rippling on the microscopic symmetry of two-dimensional materials with weak interlayer interactions and raises the possibility of approaching the paradigmatic two-dimensional Néel antiferromagnetic honeycomb lattice in MnPS3 without reaching monolayer thickness.