Crystallographic Axes Research Articles

Transverse Thermoelectric Conversion in the Mixed-Dimensional Semimetal WSi 2

Materials with axis-dependent conduction polarity are known as p×n-type or goniopolar conductors that can be used for transverse thermoelectric devices, allowing the longitudinal thermal current to be converted into the transverse electrical current. Here, we have performed experimental and computational studies on the transport properties of WSi2 single crystals, in which such axis-dependent conduction polarity of the thermopower and the Hall coefficient have recently been reported, and demonstrated the transverse thermoelectric effect by applying the temperature gradient in a direction rotated 45∘ from the crystallographic axis. We have observed strongly sample-dependent transport properties, which have also been observed in previous studies, and together with first-principles calculations we show that such sample-dependent transport properties originate from the band-dependent scattering rates of carriers. The calculated band-resolved Peltier conductivity shows that the mixed-dimensional electronic structure consisting of a quasi-one-dimensional electron Fermi surface and a quasi-two-dimensional hole surface is a key property for the axis-dependent conduction polarity. The directly obtained transverse thermoelectric figure of merit is comparable to that of the anomalous Nernst materials, implying that the present material is a potential candidate for transverse thermoelectric conversion. Published by the American Physical Society 2024

Crystal structure of the heterometallic complex of Co(II) and Nd(III) with phenanthroline

A new heterometallic complex of CoII and NdIII with phenathroline [Co(Рhen)3][Nd(NO3)5(H2O)][Nd(NO3)4(H2O)2]H2O was synthesized for the first time by the self-assembly method. The crystal structure of the complex was determined by X-ray crystallography. The compound is an anion-cation complex and crystallizes in the monoclinic space group P21/n with unit cell parameters a=12.4251(4) Å, b=11.7206(3) Å, c=36.5374(12) Å, ==900, =90.581(3)0. In the crystalline phase, the complex is in the form of a crystal hydrate with a composition of 1:1. The anionic part of the complex consists of two nitrate hydrated NdIII complexes: [Nd(NO3)5(H2O)]2– and [Nd(NO3)4(H2O)2]–, in which the coordination number of neodymium is 11 and 10, respectively. The [Co(Phen)3]3+ ion is a cationic part of the complex in which the CoII atom has a distorted CoN6 octahedral environment, bidentately coordinating three phenanthroline molecules. Due to intermolecular hydrogen bonds (N–HO, O–HO), a three-dimensional supramolecular architecture is formed in the crystal, in which the polymer layers are packed parallel along the crystallographic axis a.

LiLnGeS4 (Ln=La-Nd): Designing High Performance Infrared Nonlinear Optical Sulfides through "Band Reformation of AGS".

AgGaS2 (AGS) is the most commonly used commercial infrared nonlinear optical (IR NLO) material. However, AGS has a narrow band gap (Eg=2.58 eV) and a low laser-induced damage threshold (LIDT), primarily attributed to its mobile liquid-like Ag+ constituent and the unstable Ag-S chemical bond. Herein, we propose a "band reformation of AGS" strategy, which leads to the successful syntheses of four lanthanide sulfides, LiLnGeS4 (Ln=La-Nd), crystalizing in an asymmetric Ama2 structure. LiLaGeS4 demonstrates that eliminating the presence of Ag-4d band increases the Eg to 3.32 eV and enhances the LIDT (14-29×AGS, measured by both powder and single crystal); while increasing the nonbonding density of states of the S-3p band enhances the 2nd-nonlinear optical coefficient (1.06×AGS). Besides, the bond length discrepancy between [LiS4], [GeS4] and [LaS8] units leads to a moderate birefringence (Δn=0.052). Such a unique structure further results in extremely small thermal expansion with αL=0.41-1.74×10-5 K-1, along different crystallographic axes. Our theoretical studies indicate that the synergy of the structure building units contribute to the second harmonic generation performance. These results suggest that the "band reformation of AGS" strategy provides effective guidance to discover new NLO crystals with optimized performance.

LiLnGeS4 (Ln=La−Nd): Designing High Performance Infrared Nonlinear Optical Sulfides through “Band Reformation of AGS”

AbstractAgGaS2 (AGS) is the most commonly used commercial infrared nonlinear optical (IR NLO) material. However, AGS has a narrow band gap (Eg=2.58 eV) and a low laser‐induced damage threshold (LIDT), primarily attributed to its mobile liquid‐like Ag+ constituent and the unstable Ag−S chemical bond. Herein, we propose a “band reformation of AGS” strategy, which leads to the successful syntheses of four lanthanide sulfides, LiLnGeS4 (Ln=La−Nd), crystalizing in an asymmetric Ama2 structure. LiLaGeS4 demonstrates that eliminating the presence of Ag‐4d band increases the Eg to 3.32 eV and enhances the LIDT (14–29×AGS, measured by both powder and single crystal); while increasing the nonbonding density of states of the S‐3p band enhances the 2nd‐nonlinear optical coefficient (1.06×AGS). Besides, the bond length discrepancy between [LiS4], [GeS4] and [LaS8] units leads to a moderate birefringence (Δn=0.052). Such a unique structure further results in extremely small thermal expansion with αL=0.41–1.74×10−5 K−1, along different crystallographic axes. Our theoretical studies indicate that the synergy of the structure building units contribute to the second harmonic generation performance. These results suggest that the “band reformation of AGS” strategy provides effective guidance to discover new NLO crystals with optimized performance.

How Do Gepotidacin and Zoliflodacin Stabilize DNA Cleavage Complexes with Bacterial Type IIA Topoisomerases? 1. Experimental Definition of Metal Binding Sites.

One of the challenges for experimental structural biology in the 21st century is to see chemical reactions happen. Staphylococcus aureus (S. aureus) DNA gyrase is a type IIA topoisomerase that can create temporary double-stranded DNA breaks to regulate DNA topology. Drugs, such as gepotidacin, zoliflodacin and the quinolone moxifloxacin, can stabilize these normally transient DNA strand breaks and kill bacteria. Crystal structures of uncleaved DNA with a gepotidacin precursor (2.1 Å GSK2999423) or with doubly cleaved DNA and zoliflodacin (or with its progenitor QPT-1) have been solved in the same P61 space-group (a = b ≈ 93 Å, c ≈ 412 Å). This suggests that it may be possible to observe the two DNA cleavage steps (and two DNA-religation steps) in this P61 space-group. Here, a 2.58 Å anomalous manganese dataset in this crystal form is solved, and four previous crystal structures (1.98 Å, 2.1 Å, 2.5 Å and 2.65 Å) in this crystal form are re-refined to clarify crystal contacts. The structures clearly suggest a single moving metal mechanism-presented in an accompanying (second) paper. A previously published 2.98 Å structure of a yeast topoisomerase II, which has static disorder around a crystallographic twofold axis, was published as containing two metals at one active site. Re-refined coordinates of this 2.98 Å yeast structure are consistent with other type IIA topoisomerase structures in only having one metal ion at each of the two different active sites.

Synthesis and structure of trans-2,5-dimethylpiperazine-1,4-diium dihydrogen diphosphate

In the title salt, C6H16N2 2+ ·H2P2O7 2−, the complete dication is generated by a crystallographic centre of symmetry with the methyl groups in equatorial orientations. The complete dianion is generated by a crystallographic twofold axis with the central O atom lying on the axis: the P—O—P bond angle is 135.50 (12)°. In the crystal, the dihydrogen diphosphate anions are linked by O—H...O hydrogen bonds, generating (001) layers. The organic cations bond to the inorganic layers by way of N—H...O and C—H...O hydrogen bonds. A Hirshfeld surface analysis shows that the most important contributions for the crystal packing are from O...H/H...O (60.5%) and H...H (39.4%) contacts.

Tri-axial magnetic alignment and magnetic anisotropies in misfit-layered calcium-based cobaltites doped with rare-earth ions

In this study, we introduce an original method for quantifying tri-axial magnetic anisotropy in [Ca2CoO3-δ]0.62CoO2, and its rare earth (RE)-doped variants, [(Ca1-xREx)2CoO3-δ]0.62CoO2, utilizing a modulated rotating magnetic field of 10 T. Our findings reveal a significant correlation between the magnetic anisotropy and local structure of RE ions, particularly bond lengths and coordination numbers, which influence the magnetization axes of these magnetically aligned powders. We introduce an analytical methodology employing linear equations to calculate the magnetic susceptibilities along distinct crystallographic axes, enabling the prediction of tri-axial magnetic anisotropies at elevated concentrations of Er ions. This research not only advances our understanding of magnetic anisotropy control but also paves the way for the successful fabrication of triaxially-aligned ceramics using magneto-science techniques.

Simultaneous vector magnetometry based on fluorescence polarization of NV centers ensemble in diamond

The nitrogen-vacancy (NV) centers ensemble has extensive application prospects in vector-magnetic-field measurement due to its accurate and fixed spatial orientations along the crystallographic axes of diamonds. However, to address signals of NV centers along all four axes, a large bias magnetic field sufficient to spectrally separate their resonances is typically inevitable, which may affect the magnetic substance under test and require multiple-frequency microwaves to interrogate signals of the four axes. Here, we demonstrate an NV-based simultaneous vector magnetometer that works at a bias field as low as just separating the resonant peaks of |ms=±1 states and utilizes a single-frequency microwave. By simultaneously detecting the fluorescence at specific optical polarization angles in three orthogonal directions and determining the transformation matrix in advance, all the Cartesian components of the magnetic field under test are distinguished. The experimentally achieved magnetic-field sensitivity is 63 nT/Hz, and the bias field is reduced to around 11 Gauss (still reducible by narrowing the linewidth) in ambient conditions. The proposed methods dramatically reduce the bias field for NV-based simultaneous vector magnetometers and potentially expand their applications in biological science, materials science, and industrial noninvasive detection.

Quantum size effects in ultra-thin YBa2Cu3O7 − x films

The d-wave symmetry of the order parameter with zero energy gap in nodal directions stands in the way of using high-temperature superconductors for quantum applications. We investigate the symmetry of the order parameter in ultra-thin YBa2Cu3O7 − x (YBCO) films by measuring the electrical transport properties of nanowires aligned at different angles relative to the main crystallographic axes. The anisotropy of the nanowire critical current in the nodal and antinodal directions reduces with the decrease in the film thickness. The Andreev reflection spectroscopy of the nanoconstrictions shows the presence of a thickness-dependent energy gap that does not exist in bulk YBCO. We find that the thickness-dependent energy gap appears due to the quantum size effects in ultra-thin YBCO films that open the energy gap along the entire Fermi surface. The fully gapped state of the ultra-thin YBCO films makes them a promising platform for quantum applications, including quantum computing and quantum communications.

ELECTROMECHANICAL PROGRAMMER FOR ACOUSTOELECTRONIC SENSORS OF PHYSICAL QUANTITIES

An electromechanical programmer is described, intended for programming an acoustoelectronic angular displacement meter, constructed on the basis of the effect of dependence of the phase velocity of surface acoustic waves on the direction of propagation relative to the crystallographic axis of a piezoelectric sound conductor.

Crystal Growth of LiNa5Mo9O30 Crystals of High Optical Quality

The bulk of the LiNa5Mo9O30 (LNM) crystals were successfully grown in the [010] and [001] directions without internal inclusions and cracks, using the Czochralski method with a low temperature gradient. The crystal grown in the [010] direction showed a tendency to twinning. The crystal grown in the [001] direction demonstrated high structural perfection (FWHM = 13″) for the (001) plane and high optical quality Δn ≈ 2 × 10−5. The laser-induced damage threshold was measured along a, b and c axes and was 12.2, 27.0 and 27.5 J/cm2, respectively. The thermo-optical coefficient dn/dT was measured for the main crystallographic axes, which was −5.75 × 10−6, −20.2 × 10−6 and 3.65 × 10−6 K−1 along the a, b and c axes, respectively. The second harmonic generation (SHG) was conducted in the crystalline LNM sample. The maximum efficiency value of 3.5% at a pump power of 12 W was achieved.

Anisotropy-driven magnetic phase transitions in SU(4)-symmetric Fermi gas in three-dimensional optical lattices

Abstract We study SU(4)-symmetric ultracold fermionic mixture in the cubic optical lattice with the variable tunneling amplitude along one particular crystallographic axis in the crossover region from the two- to three-dimensional spatial geometry. To theoretically analyze emerging magnetic phases and physical observables, we describe the system in the framework of the Fermi-Hubbard model and apply dynamical mean-field theory. We show that in two limiting cases of anisotropy there are two phases with different antiferromagnetic orderings in the zero temperature limit and determine a region of their coexistence. We also study the stability regions of different magnetically-ordered states and density profiles of the gas in the harmonic optical trap.

Crystal structure of propane-1,3-diaminium squarate dihydrate.

Propane-1,3-diaminium squarate dihydrate, C3H12N2 2+·C4O4 2-·2H2O, results from the proton-transfer reaction of propane-1,3-di-amine with squaric acid and subsequent crystallization from aqueous medium. The title compound crystallizes in the tetra-gonal crystal system (space group P4bm) with Z = 2. The squarate dianion belongs to the point group D 4h and contains a crystallographic fourfold axis. The propane-1,3-diaminium dication exhibits a C 2v -symmetric all-anti conformation and resides on a special position with mm2 site symmetry. The orientation of the propane-1,3-diaminium ions makes the crystal structure polar in the c-axis direction. The solid-state supra-molecular structure features a triperiodic network of strong hydrogen bonds of the N-H⋯O and O-H⋯O types.

Magnetic anisotropy of L1[formula omitted] FeNi (001), (010), and (111) ultrathin films: A first-principles study

In previous experiments, L10 FeNi thin films with different surfaces, including (001), (110), and (111), were produced and studied. Each surface defines a different alignment of the crystallographic tetragonal axis with respect to the film’s plane, resulting in different magnetic anisotropies. In this study, we use density functional theory calculations to examine three series of L10 FeNi films with surfaces (001), (010), and (111), and with thicknesses ranging from 0.5 to 3 nm (from 4 to 16 atomic monolayers). Our results show that films (001) have perpendicular magnetic anisotropy, while (010) favor in-plane magnetization, with a clear preference for the tetragonal axis [001]. We proposed calling this type of in-plane anisotropy fixed in-plane. A film with a surface (111) and a thickness of four atomic monolayers has a magnetization easy axis almost perpendicular to the plane of the film. As the thickness of the (111) film increases, the direction of magnetization rotates towards a tetragonal axis [001], positioned at an angle of about 45° to the plane of the film. Furthermore, the most significant changes in spin and orbital magnetic moments occur at a depth of about three near-surface atomic monolayers. Ultrathin L10 FeNi films with varying magnetic anisotropies may find applications in spintronic devices.

Investigations of magnetic and thermal expansion properties of two cobalt(II) metal-organic frameworks constructed by mixed bipyridyl-tetracarboxylate strategy

We report the syntheses, crystal structures, adsorption behavior, thermal expansion behavior, and magnetic properties of two cobalt(II) metal-organic frameworks (MOFs), {[Co(btca)1/2(bpe)(H2O)2]·bpe}n (1) and {Co(btca)1/2(bpe)(DMF)}n (2, H4btca = 1,2,4,5-benzenetetracarboxylic acid; bpe = 1,2-di(4-pyridyl)ethane), constructed using mixed bipyridyl and tetracarboxylate ligands. Single-crystal X-ray diffraction (SC-XRD) indicates that the change of synthetic solvents leads to a significant tuning of structural dimensionality from 2D to 3D framework. Temperature-dependent SC-XRD reveals anisotropically negative and positive thermal expansion of the compounds identified along different crystallographic axes within the frameworks over a 120–400 K temperature range. N2 adsorption measurements indicate a nonporous and ultramicroporous framework for 1 and 2, respectively. Magnetic measurements indicate an easy-plane magnetic anisotropy of the Co2+ ions in the MOFs, with experimental D values of 63.1 and 87.1 cm−1. The ac susceptibility measurements of 1 and 2 show field-induced slow magnetic relaxation below 6 K through different relaxation dynamics. This work not only provides two new cobalt(II) SIM-MOFs, but also presents an effective bipyridyl-tetracarboxylate strategy for designing and building framework materials with interesting magnetic and mechanical properties.

Two orientation effects and large anisotropy of parameters in piezo-active 2–1–2 composites based on [0 1 1]-poled crystals

The results of a comparative study on piezo-active 2–1–2 composites with two ferroelectric components are discussed. The composite structure combines elements of 2–2 (laminar) and 1–3 (fibrous) connectivity patterns. The first component in each composite is domain-engineered [0 1 1]-poled single crystal with macroscopic mm2 symmetry and high piezoelectric activity. The second component is a poled ferroelectric ceramic that is represented by parallel rods in the shape of an elliptic cylinder with a large ratio of semi-axes at its base. The first orientation effect is appreciable due to rotations of the main crystallographic axes X and Y around Z || OX 3 by an angle α in each crystal layer. Rotation of the ceramic rod bases by an angle γ in a polymer medium leads to the second orientation effect in the 2–1–2 composite. The two orientation effects contribute to a large anisotropy of electromechanical coupling factors k3j∗ , energy-harvesting figures of merit (FOM) (Q3j∗)2 and modified FOM F3j∗σ for a stress-driven harvester. The large level of (Q32∗)2 , (Q33∗)2 , F32∗σ and F33∗σ (these parameters are of the order of 10−11–10−10 Pa−1) indicates that the studied composites are suitable for piezoelectric sensors, transducers and energy-harvesting systems. New m—α diagrams put forward in the present study show regions wherein the large anisotropy of the effective parameters ( |k33∗ / k3f∗|⩾5 , (Q33∗/Q3f∗ )2 ⩾10 and F33∗σ/F3f∗σ⩾10 , f = 1 and 2) is achieved when changing the volume fraction m of the single crystal and the rotation angle α. As a result, the leading role of the first orientation effect is emphasised.

Gemological Characteristics of Blue-Violet Cordierite

Cordierite is a violet-blue gem mineral primarily composed of magnesium aluminum silicate. This study employed three samples of Mg-cordierite and conducted tests on their gemological characteristics, spectroscopic features, and chemical composition using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, ultraviolet spectrophotometry, X-ray photoelectron spectroscopy (XPS), and electron microprobe. The study also explored and analyzed the polychroism and coloration mechanisms of the samples. The results indicate that the lattice vibrations of the Mg-cordierite samples differ along the directions parallel to the a, b, and c crystallographic axes, leading to certain variations in spectral characteristics among these directions. The article provides experimental evidence for the reasons for the polychroism of cordierite in different crystal axes, which is of great significance in the quality evaluation of cordierite.

Controlling the columnar-to-equiaxed transition and crack propagation behavior of laser welded Al–Li alloy reinforced with TiC nanoparticles

The predominant method for improving the mechanical characteristics of aluminum-lithium (Al–Li) alloys during laser welding is by regulating the transition from columnar crystals to equiaxed crystals. The transition is facilitated through the incorporation of TiC particles, which play a crucial role in augmenting the strength and toughness of the aluminum alloy. The inclusion of TiC particles offers a new opportunity to enhance the utilization of Al–Li alloys in laser welding procedures. The main aim of this study is to control the transition from columnar to equiaxed crystal structures by creating a TiC nanoparticle-reinforced aluminum alloy filler wire. This is intended to improve the properties of laser-welded joints. The study investigates the impact of different TiC particle contents on the microstructural characteristics. The presence of TiC particles is noted to enhance the transformation of columnar crystals into equiaxed crystals in the welded joints, resulting in a refined microstructure. The augmentation of particle content results in a notable reduction in the average grain size, decreasing from 78.25 μm to 37.15 μm. This alteration shifts the directional growth preference from specific crystallographic axes to a stochastic trajectory. Significantly, when the particle content reaches 0.6 wt%, remarkable enhancements in both tensile strength and elongation are evident, resulting in an ultimate tensile strength of 318 MPa and an elongation of 4.8 %. The dispersed configuration of TiC particles plays a pivotal role in hindering the movement of dislocations, consequently increasing the energy necessary for this mechanism. Moreover, the existence of these particles at grain boundaries impedes the propagation of cracks by altering the direction of the crack path, absorbing additional energy, and consequently improving toughness. An evident pattern emerges when examining higher particle concentrations, indicating that a decrease in ultimate tensile strength is concomitant with an increase in elongation.

Application, structure, salts and complexes of lidocaine: a review. Part V. structure of bis(lidocaine) tetrachloridocuprate(II)

The review focuses on lidocaine (2-(diethylamino)-N-(2,6-dimethylphenyl)acetamide): in the first part, its use in various branches of medicine, as well as the structure of lidocaine, its salts and molecular complexes was discussed; in the second part the use of lidocaine in the composition of deep-eutectic solvents (DES), DES-microemulsions and complexes of lidocaine with zinc, copper, cobalt, platinum and iron was considered; in the 3rd the structure of bis(lidocaine) tetrachlorido-zincate(II) was considered, in the 4th part the structure of bis(lidocaine) tetrachloridoferrate(III) chloride was discussed, this part reports on the synthesis and structure of bis(lidocaine) tetra-chloridocuprate(II), (LidH)2[CuCl4], which crystallizes in the monoclinic space group P21/c with a = 15.7831(2), b = 24.2992(2), c = 17.8748(2) Å, β = 104.874(1)°, V = 6625.58(13) Å3, Z = 8, and Dc = 1.355 Mg/m3. The coordination of the Cu2+ ions with chlorine atoms generates two differently distorted tetrahedral anions [CuCl4]2–, while four protonated cations LidH+ remain in an outer coordination sphere. Anions and cations are associated by hydrogen bonds of the N–H···Cl type to form the 2{(LidH)2[CuCl4]} dimer, in which the distance between two copper atoms is 8.95 Å (c/2). With the help of hydrogen bonds of the type N–H···O and N–H·Cl, each dimer is connected with four neighboring dimers, resulting in a three-dimensional structure in which dimers lie at an angle of 28.39° to the a crystallographic axis in the ab planes located at a distance of 10.67 Å from each other.

Effect of Solvent Composition on Non-DLVO Forces and Oriented Attachment of Zinc Oxide Nanoparticles.

Oriented attachment (OA) occurs when nanoparticles in solution align their crystallographic axes prior to colliding and subsequently fuse into single crystals. Traditional colloidal theories such as DLVO provide a framework for evaluating OA but fail to capture key particle interactions due to the atomistic details of both the crystal structure and the interfacial solution structure. Using zinc oxide as a model system, we investigated the effect of the solvent on short-ranged and long-ranged particle interactions and the resulting OA mechanism. In situ TEM imaging showed that ZnO nanocrystals in toluene undergo long-range attraction comparable to 1kT at separations of 10 nm and 3kT near particle contact. These observations were rationalized by considering non-DLVO interactions, namely, dipole-dipole forces and torques between the polar ZnO nanocrystals. Langevin dynamics simulations showed stronger interactions in toluene compared to methanol solvents, consistent with the experimental results. Concurrently, we performed atomic force microscopy measurements using ZnO-coated probes for the short-ranged interaction. Our data are relevant to another type of non-DLVO interaction, namely, the repulsive solvation force. Specifically, the solvation force was stronger in water compared to ethanol and methanol, due to the stronger hydrogen bonding and denser packing of water molecules at the interface. Our results highlight the importance of non-DLVO forces in a general framework for understanding and predicting particle aggregation and attachment.