Macromolecular crystallography at cryogenic temperatures has so far provided the majority of the experimental evidence that underpins the determination of the atomic structures of proteins and other biomolecular assemblies by means of single crystal X-ray diffraction experiments. One of the core limitations of the current methods is that crystal samples degrade as they are subject to X-rays, and two broad groups of effects are observed: global and specific damage. While the currently successful approach is to operate outside the range where global damage is observed, specific damage is not well understood and may lead to poor interpretation of the chemistry and biology of the system under study. In this work, we present a phenomenological model in which specific damage is understood as the result of a single process, the steady excitation of crystal electrons caused by X-ray absorption, which acts as a trigger for the bulk effects that manifest themselves in the form of global damage and obscure the interpretation of chemical information from XFEL and synchrotron structural research. Full article

Three polyhydroxyl-bridged tetranuclear Mn^III complexes [Mn₄(L^1a)₂(μ₃-OMe)₂(μ₂-OMe)₂(MeOH)₂] (1), [Mn₄(L^2a)₂(μ₃-OMe)₂(μ₂-OMe)₂(H₂O)₂] (2), and [Mn₄(L^3a)₂(μ₃-OMe)₂(μ₂-OMe)₂(H₂O)₂] (3) derived from Mnⁿ⁺-promoted reactivity of Schiff base ligands (HL¹ = 1-(4-{[(E)-3,5-dichlorine-2-hydroxybenzylidene]amino}phenyl)ethanone O-benzyloxime, HL² = 1-(4-{[(E)-3-bromine-5-chloro-2-hydroxybenzylidene]amino}phenyl) ethanone O-benzyloxime, and HL³ = 1-(4-{[(E)-3,5-dibromine-2-hydroxybenzylidene]amino}phenyl)ethanone O-benzyloxime) have been synthesized and characterized. In the Mn^III complexes 1, 2, and 3, the newly formed ligands (L^1a)⁴⁻, (L^2a)⁴⁻, and (L^3a)⁴⁻ are derived from the chemoselective cleavage of the C=N bond in the original Schiff base ligands HL¹, HL², and HL³ to form corresponding halogenated salicylaldehyde, 3,5-dichlorosalicylaldehyde, 3-bromine-5-chlorosalicylaldehyde, and 3,5-dibrominesalicylaldehyde, respectively. Then, the further addition of acetone to two halogenated salicylaldehyde molecules in situ α,α double aldol reaction promoted by Mnⁿ⁺ ions in the presence of base to give the new ligands ((L^na)⁴⁻. X-ray crystallographic analyses of the Mn^III complexes 1, 2, and 3 show that the three complexes are all tetranuclear structure and crystallizes in the triclinic system, space group P-1. The four Mn^III ions and bridging alkoxido groups are arranged in a face-shared dicubane-like core with two missing vertices. In the three Mn^III complexes, the asymmetric unit contains two kinds of different Mn^III ions (Mn1 and Mn2), where the Mn^III ions are all hexacoordinated with slightly distorted octahedral geometries. Simultaneously in the synthesis of multinuclear Mnⁿ⁺ complexes above, we explored the crystal structure, spatial configuration, and spectroscopic properties of the multinuclear Mn^III complexes with different halogen substituents. Full article

In order to make a rational design of magnesium alloys for bone repair, four kinds of Mg alloy ingots were prepared by vacuum induction furnace, namely Mg-3Zn-0.2Ca (wt.%) (ZX30), Mg-3Zn-0.8Zr (wt.%) (ZK30), Mg-3Zn-0.8Zr-0.3Sr (wt.%) (ZKJ300) and Mg-3Zn-0.8Zr-0.3Ca-0.3Ag (wt.%) (ZKXQ3000) alloys. The four ingots were extruded into bar materials through a hot-extrusion process under different temperatures with different extrusion ratios, the mechanical performances and the corrosion behaviors in the simulated body fluid (SBF) of the four alloys were investigated, and the mechanism of fracture and corrosion was characterized by scanning electron microscopy (SEM). The results showed the ultimate compressive strength (UCS) of all the alloys were found to be around 360 MPa, while ultimate tensile strengths (UTS) of ZKJ300 (334.61 ± 2.92 MPa) and ZKXQ3000 (337.56 ± 2.19 MPa) alloys were much higher than those of ZX30 (298.17 ± 0.93 MPa) and ZK30 (293.26 ± 2.71 MPa) alloys. The electrochemical noise and immersion tests in the SBF indicated that ZK30 alloy performed better in corrosion resistance. Full article

In this work, the crystallization behaviors, such as degree of crystallinity and crystalline thickness of poly(ε-caprolactone) (PCL) matrix with the incorporation of graphene oxide (GO) and their evolution with time were examined in order to better understand the influences of residual groups of GO on the semi-crystalline polyester. The results showed that the residual strong oxidizing debris on the GO surface could induce the degradation of amorphous parts in PCL matrix. Moreover, the increasing degree of crystallinity and almost constant crystalline thickness implies that oxidative degradation cannot degrade the crystal structure of PCL matrix. Full article

A precursor, C₂₁H₂₉NO₈ (A1) was prepared by reactions of 1,1-dimethoxy-N,N-dimethylmethanamine and 1,5-dioxaspiro[5.5]undecane-2,4-dione. The new N-containing heterocyclic compound, C₁₉H₁₉NO₄ (B1) was obtained by adding A1 into ethanol solution of o-toluidine. The crystal structure determination of two compounds were both found to belong to the triclinic P-1 space group. The precursor includes one (C₂H₈N)⁺ cation and one (C₁₉H₂₁O₈)⁻ anion, which constituted a chained structure by N–H···O intra- and intermolecular interactions. The title compound (B1) formed a 3D-network structure by weak C–H···O intermolecular interactions and π···π stacking interactions. The fluorescent behaviors of A1 and B1 in ethanol solution were discussed. The result shows that they exhibit blue and purplish blue emission, respectively. Full article

SrLi₂{Li[CoN₂]}, an isostructural variant of Li₄SrN₂, has been synthesised as black single crystals from a reaction between Li₂[(Li,Co)N] and Sr₂N, at 973 K using a Li flux in a sealed tantalum ampoule. Single crystal diffraction refinements gave a tetragonal unit cell, which upon closer inspection showed a monoclinic supercell. This supercell allowed, for the first time, the refinement of the occupation of metal atoms along the infinite chains in the structure, resulting in the chemical formula SrLi₂{Li_0.65Co_0.35[Co_0.65Li_0.35N₂]}. This revealed a clear preference for the Li and Co atoms to alternate along the chains. Magnetic measurements showed the sample to be a Curie paramagnet, with Co(I) being in a high-spin S = 1 configuration. Full article

Radiation damage represents a fundamental limit in the determination of protein structures via macromolecular crystallography (MX) at third-generation synchrotron sources. Over the past decade, improvements in both source and detector technology have led to MX experiments being performed with smaller and smaller crystals (on the order of a few microns), often using microfocus beams. Under these conditions, photoelectrons (PEs), the primary agents of radiation-damage in MX, may escape the diffraction volume prior to depositing all of their energy. The impact of PE escape is more significant at higher beam energies (>20 keV) as the electron inelastic mean free path (IMFP) is longer, allowing the electrons to deposit their energy over a larger area, extending further from their point of origin. Software such as RADDOSE-3D has been used extensively to predict the dose (energy absorbed per unit mass) that a crystal will absorb under a given set of experimental parameters and is an important component in planning a successful MX experiment. At the time this study was undertaken, dose predictions made using RADDOSE-3D were spatially-resolved, but did not yet account for the propagation of PEs through the diffraction volume. Hence, in the case of microfocus crystallography, it is anticipated that deviations may occur between the predicted and actual dose absorbed due to the influence of PEs. To explore this effect, we conducted a series of simulations of the dose absorbed by micron-sized crystals during microfocus MX experiments. Our simulations spanned beam and crystal sizes ranging from 1μm to 5μm for beam energies between 9 keV and 30 keV. Our simulations were spatially and temporarily resolved and accounted for the escape of PEs from the diffraction volume. The spatially-resolved dose maps produced by these simulations were used to predict the rate of intensity loss in a Bragg spot, a key metric for tracking global radiation damage. Our results were compared to predictions obtained using a recent version of RADDOSE-3D that did not account for PE escape; the predicted crystal lifetimes are shown to differ significantly for the smallest crystals and for high-energy beams, when PE escape is included in the simulations. Full article

A series of Hf:Yb:Nd:LiNbO₃ crystals with different [Li]/[Nb] ratios (0.946, 1.05, 1.20, and 1.38) were grown using the Czochralski method. X-ray diffraction phase results of the samples show that the LiNbO₃ doped Hf⁴⁺, Yb³⁺, and Nd³⁺ only have a slight change in the lattice constant. The birefringence gradient of the HfYbNd4 sample measured using the birefringence gradient method was 3.3 × 10⁻⁵ ∆R/cm⁻¹, which was the best optical uniformity. The optical damage resistance ability was measured using the light-induced scattering exposure energy flus threshold method. When the [Li]/[Nb] ratios in the melt achieve 1.38, the exposure energy achieves 120.74 J/cm², which is approximately 87 times higher than HfYbNd1. Full article

Melamine (C₃H₆N₆; 1,3,5-triazine-2,4,6-triamine) is an aromatic substituted s-triazine, with carbon and nitrogen atoms forming the ring body, and amino groups bonded to each carbon. Melamine is widely used to produce laminate products, adhesives, and flame retardants, but is also similar chemically and structurally to many energetic materials, including TATB (2,4,6-triamino-1,3,5- trinitrobenzene) and RDX (1,3,5-trinitroperhydro-1,3,5-triazine). Additionally, melamine may be a precursor in the synthesis of superhard carbon-nitrides, such as β-C₃N₄. In the crystalline state melamine forms corrugated sheets of individual molecules, which are stacked on top of one another, and linked by intra- and inter-plane N-H hydrogen bonds. Several previous high-pressure X-ray diffraction and Raman spectroscopy studies have claimed that melamine undergoes two or more phase transformations below 25 GPa. Our results show no indication of previously reported low pressure polymorphism up to approximately 30 GPa. High-pressure crystal structure refinements demonstrate that the individual molecular units of melamine are remarkably rigid, and their geometry changes very little despite volume decrease by almost a factor of two at 30 GPa and major re-arrangements of the intermolecular interactions, as seen through the Hirshfeld surface analysis. A symmetry change from monoclinic to triclinic, indicated by both dramatic changes in diffraction pattern, as well as discontinuities in the vibration mode behavior, was observed above approximately 36 GPa in helium and 30 GPa in neon pressure media. Examination of the hydrogen bonding behavior in melamine’s structure will allow its improved utilization as a chemical feedstock and analog for related energetic compounds. Full article

The majority of tunable liquid crystal devices are driven by electric fields. The performance of such devices can be altered by the presence of small amounts of ions in liquid crystals. Therefore, the understanding of possible sources of ions in liquid crystal materials is very critical to a broad range of existing and future applications employing liquid crystals. Recently, nanomaterials in liquid crystals have emerged as a hot research topic, promising for its implementation in the design of wearable and tunable liquid crystal devices. An analysis of published results revealed that nanodopants in liquid crystals can act as either ion-capturing agents or ion-generating objects. In this paper, a recently developed model of contaminated nanomaterials in liquid crystals is analyzed. Nanoparticle-enabled ion capturing and ion generation regimes in liquid crystals are discussed within the framework of the proposed model. This model is in very good agreement with existing experimental results. Practical implications and future research directions are also discussed. Full article

Bioinspired self-assembled composite materials are appealing both for their industrial applications and importance in natural sciences, and represent a stimulating topic in the area of materials science, biology, and medicine. The function of the organic matrix has been studied from the biological, chemical, crystallographic, and engineering point of view. Little attention has been paid to the effect of one of the two main components of the organic matrix, the sericin fraction, on the growth morphology of calcium carbonate polymorphs. In the present work, we address this issue experimentally, emphasizing the morphological effects of sericin on calcite and aragonite crystals, and on the formation of a sericin-aragonite-calcite self-assembled composite with a hierarchic structure comparable to that of natural nacre. Full article

Double-sided planetary grinding as an efficient and precise machining method is used for the rapid thinning and flattening process of sapphire substrate. As an intermediate processing technology of sapphire substrate preparation procedure, many experiments are carried out to evaluate the lapping effect in the paper. Surface quality, processing efficiency, and surface dent depth, which all impact subsequent polishing processes, are evaluated. Firstly, the four stages of grinding process are analyzed to display the surface accuracy changing process of the sapphire substrates during grinding. Secondly, the effect of three main grinding parameters (grinding pressure, rotation speed of the grinding wheels, and the grain size of grinding wheels) on surface accuracy and processing efficiency are investigated. Finally, sapphire removal rate of about 10 µm/min is achieved easily at the optimized condition with a good surface quality by double-sided planetary grinding. The double-sided planetary grinding with the ceramic-bonded diamond wheel is suitable for the rapid thinning and flattening of the sapphire substrate. Full article

Effect of Zr content on the structure and water–gas shift reaction catalytic activities of Au-CeO₂-ZrO₂ catalysts were quantitatively analyzed in detail. For the low ZrO₂ content (0–15 wt. %), the Ce-Zr-O solid solutions were formed through the substitutional incorporation of Zr cations into CeO₂ lattice, resulting in the contraction of cell parameters a and d-spacing (i.e., lattice distortion) and the increase of microstrain and oxygen vacancies. Quantitatively, the enhanced WGS activities have good linear correlation with the cell parameters a, microstrain, Raman shift and oxygen vacancies. Whereas, for the rich-zirconia (45 wt. %) sample, Au-CeZr-45 has some isolated t-ZrO₂ and fluorite CeO₂ instead of solid solution. The isolated t-ZrO₂ crystallites block the contact between Au and CeO₂, resulting in the agglomeration of gold clusters and, as a consequence, poor WGS activity of Au-CeZr-45 catalyst. Full article

In this study, the inverse temperature crystallization method was used to produce bulk crystal CH₃NH₃PbBr₃ (MAPbBr₃) perovskite, and repeated crystallization processes were carried out to obtain a larger crystal size and develop a bulk material for application in semiconductor devices. The material and optoelectronic properties of the MAPbBr₃ perovskite crystals after the repeated processes were characterized. The X-ray diffraction (XRD) patterns of all samples demonstrated a pure perovskite phase. One strong diffraction peak located at 29.4°, which corresponds to the (200) perovskite plane, was observed after the first growth cycle. The mobilities for the samples after the first, second, and third growth cycles were calculated and resulted to be 0.9, 5.6, and 54.7 cm²/Vs, respectively, according to Mott–Gurney law. A higher mobility after the multiple crystallization processes indicated that the surface states caused by voids in the crystals favored electron transition in the perovskite material. Full article

A homotrinuclear Zn^II bis(salamo) coordination compound, [LZn₃(OAc)₂(H₂O)] of a new bis(salamo)-like ligand, has been synthesized and structurally characterized using elemental analyses, IR, UV-Vis and fluorescent spectra, and Hirshfeld surface analysis. Hirshfeld surface analyses and X-ray crystallography revealed that complexation between Zn^II acetate dihydrate and the ligand H₄L afforded a 3:1 (Zn^II:L) type coordination compound. Moreover, the X-ray crystal structure analysis demonstrated that two μ₂-acetate anions bridge three Zn^II atoms in a μ₂-fashion forming a homo-trinuclear structure. There were two kinds of Zn^II atoms coordination geometries (strongly distorted square pyramidal (Zn1) and distorted trigonal bipyramidal (Zn2 and Zn3)) in the Zn^II coordination compound. In addition, a 3D supra-molecular structure was constructed by intermolecular C-H···π and π···π interactions in the Zn^II coordination compound. Most importantly, the fluorescent and antimicrobial properties of H₄L and its Zn^II coordination compound were investigated. Full article