High-resolution X-ray Diffraction Data Research Articles

Al-Si Order and Chemical Composition Model across Scapolite Solid Solutions with Evidence from Rietveld Structure Refinements

Scapolite forms solid solutions between the end members marialite, Na4[Al3Si9O24]Cl = Me0, and meionite, Ca4[Al6Si6O24]CO3 = Me100. Al-Si order and chemical composition models are proposed for the scapolite solid solutions. These models predict the chemical composition, Al-Si order, and average <T–O> distances between Me0–Me100. These models are based on the observed order of clusters and on two solid solutions that meet at Me75 coupled with predicted chemical compositions and <T–O> distances. The [Na4·Cl]3+ and [NaCa3·CO3]5+ clusters are ordered between Me0–Me75, whereas the clusters [NaCa3·CO3]5+ and [Ca4·CO3]6+ are disordered from Me75–Me100. To confirm the structural model, the crystal structure of 27 scapolite samples between Me6–Me93 has been obtained using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinements. The structure was refined in space group P42/n for all the samples. The <T–O> distances indicate that the T1 (=Si), T2 (=Al), and T3 (=Si) sites are completely ordered at Me37.5, where the 1:1 ratio of [Na4·Cl]3+:[NaCa3·CO3]5+ clusters are ordered and gives rise to antiphase domain boundaries (APBs) based on Cl-CO3 order instead of Al-Si order. The presence of APBs based on Cl-CO3 order and cluster order indicate that neither space group P42/n nor I4/m are correct for the structure of scapolite, but the lower symmetry space group P42/n is a good approximation for modeling the average structure of scapolite. The complete Al-Si order at Me37.5 changes in a regular and predictable manner toward the end members: Me0, Me75, and Me100. The observed unit cell and several structural parameters show a discontinuity at Me75, where the series is divided into two. There is no structural evidence to support any phase transition in the scapolite series. The T1 site contains only Si from Me0–Me37.5; from Me37.5–Me100, Al atoms enter the T1 site and the <T1–O> distance increases linearly to Me100.

A process-based geochemical framework for carbonate sediments during marine diagenesis

A significant proportion of marine calcium carbonate sediments are comprised of metastable minerals that are susceptible to diagenetic alterations during burial. These reactions can reset the geochemical signature of sediments and pore fluids and influence elemental cycling in the ocean. However, the timing and mechanisms by which these reactions take place are poorly constrained. This study uses cores drilled on the slope of the Great Bahama Bank to provide quantitative constraints on important diagenetic reactions; namely respiration-driven dissolution, authigenic carbonate mineral formation, and conversion of aragonite to low Mg calcite (LMC). We perform detailed mineralogical characterization using newly acquired, high resolution X-ray diffraction (XRD) data and over 1000 reanalyzed XRD scans, characterize sediments texturally and elementally using electron microprobe data, calculate pore fluid saturation state with respect to aragonite using a Pitzer ion interaction approach, and use pore fluid chemistry and experimental distribution coefficients to predict authigenic carbonate compositions. These data suggest that aerobic organic matter oxidation, enabled by the advection of oxygenated seawater throughout the upper ∼ 30 m interval of sediment, causes undersaturation and thus dissolution of biogenic high Mg calcite (HMC) and aragonite. Deeper, anaerobic organic matter oxidation takes over and causes supersaturation, promoting authigenic precipitation in the form of HMC, which in turn decreases pore fluid Mg/Ca and promotes aragonite conversion to LMC. One novel aspect of this study is the identification of three types of calcites using the newly acquired XRD and electron microprobe data. Based on their unique crystallographic characteristics and chemical compositions, these types of calcites are interpreted to represent pelagic biogenic LMC, bank-derived biogenic HMC, and authigenic HMC precipitated from pore fluids. Notably, the composition of the authigenic calcite matches that predicted to precipitate from pore fluids using an empirical Mg partition coefficient in calcite. Calcites that form authigenically and from aragonite via replacement are suggested to recrystallize with burial as evidenced by the decrease in Mg content and micro-strain. This process-based geochemical framework assigns diagenetic processes to a specific depth window within the sediment column and paves the way for a mechanistic understanding of carbonate diagenesis, one that is rooted in thermodynamic and kinetic bases.

Similarities and differences in the ordering at short and long ranges in a NaNbO3 based Pb-free smart system: a key to functional properties

In this study, we have investigated the crystal structure of the solid solution of antiferroelectric NaNbO3(NN) with ferroelectric Ba0.9Ca0.1TiO3(BCT), i.e. (1−x)NN- xBCT for 0⩽x⩽1.0 using High-resolution powder x-ray diffraction (HR-XRD) data, dielectric measurements in conjunction with Raman spectroscopic studies. The investigation of long-range structural phase transitions as a function of composition(x) using x-ray diffraction is complemented by short-range structural insights from Raman spectroscopy. The incorporation of BCT disrupts the delicate antiferroelectric ordering of NN and stabilizes various ferroelectric phases with increasing BCT content(x). At x = 0.10, the simultaneous presence of two ferroelectric phases viz., Pmc21 and Amm2, results in a threefold rise in remanent polarization compared to off-boundary compositions. The composition with higher BCT content (i.e. x⩾0.50 ) has shown the anomalous existence of two long-range cubic structures, both of which are characterized by Pm 3¯ m space group. In spite of having a two-phase long-range centrosymmetric structure, we have observed a slim Polarization vs. Electric field(P-E) hysteresis loop for 0.50⩽x⩽0.80 . This contrapositive behavior (i.e. hysteresis loop in a centrosymmetric structure) has been attributed to the correlations among local static polar distortions of rhombohedral type ascertained using Raman spectroscopy. The coexistence of two ferroelectric phases at room temperature(for x = 0.10) and a slim hysteresis loop (for 0.50⩽x⩽0.80 ) make these compositions potential ingredients for applications in ferroelectric memory and energy storage devices.

Shock-wave-induced variation in structural, optical and third-order nonlinear properties of an L-ascorbic acid single crystal

The utilization of shock waves plays a pivotal role in the advancement of multiple scientific domains like aerospace, defense, geology, environment, medicine and many more. They serve as essential tools in scientific investigations, enabling the exploration of material behavior under extreme conditions, viz. elevated pressure and temperature. The present study is specifically dedicated to scrutinizing the repercussions of shock waves on an L-ascorbic acid single crystal, to which they were intentionally applied to assess their influence on structural, optical and third-order nonlinearity properties. Powder X-ray diffraction analysis unveiled a discernible overall enhancement in the crystalline quality of the grown crystal following exposure to shock waves. This observation was consistently corroborated by high-resolution X-ray diffraction data, particularly on the (200) crystallographic planes. Furthermore, the optical transmittance of the crystal exhibited a notable increase upon the application of shock waves, while the material's band gap remained unaffected. In parallel, the third-order nonlinearity of the crystal was found to undergo a significant augmentation as a consequence of the shock treatment, as confirmed through Z-scan measurements. These empirical findings unequivocally demonstrate the substantial enhancement in the structural, optical and nonlinear properties of the grown crystal when subjected to shock waves, rendering it well suited for nonlinear optical applications.

Resilience of the Aurivillius structure upon La and Cr doping in a Bi5Ti3FeO15 multiferroic.

Combining the experimental techniques of high-resolution X-ray diffraction, magnetometry, specific heat measurement, and X-ray photoelectron, Raman and dielectric spectroscopy techniques, we have studied the influence of La and Cr doping on the crystal structure and magnetism of the room temperature Aurivillius multiferroic Bi5Ti3FeO15 by investigating the physical properties of (Bi4La)Ti3FeO15 and Bi5Ti3 (Fe0.5Cr0.5)O15. The parent (Bi5Ti3FeO15) and the doped ((Bi4La)Ti3FeO15 and Bi5Ti3(Fe0.5Cr0.5)O15) compounds crystallize in the A21am space group, which is confirmed through our analysis of high-resolution synchrotron X-ray diffraction data obtained on phase-pure polycrystalline powders. We determined the oxidation states of the metal atoms in the studied compounds as Fe3+, Ti4+, Cr3+, and La3+ through the analysis of X-ray photoelectron spectroscopy data. The magnetic susceptibilities of the three compounds are marked by the absence of a long-range ordered ground state, but dominated by superparamagnetic clusters with dominant antiferromagnetic interactions. This signature of short-range magnetism is also seen in specific heat as a low temperature enhancement which is suppressed upon the application of external magnetic fields up to 8 T. Our dielectric spectroscopy experiments showed that the three studied compounds display similar features in the dielectric constant measured as a function of frequency. However, upon doping La at the Bi site, the width of the ferroelectric hysteresis loop increases for (Bi4La)Ti3FeO15 compared to that of the parent compound Bi5Ti3FeO15, and with Cr doping, Bi5Ti3(Fe0.5Cr0.5)O15 becomes a leaky dielectric. The resilience of the Aurivillius crystal structure towards doping of La at the Bi site and Cr at the Fe site is clearly seen in the bulk properties of magnetic susceptibility, specific heat and the average crystal structure. The relevance of changes in the local structure is evident from our Raman spectroscopy and X-ray pair distribution function studies.

Multiple unconventional charge density wave transitions in LaPt2Si2 superconductor clarified with high-energy X-ray diffraction

The quasi-2D platinum-based rare earth intermetallic LaPt2Si2 has attracted attention as it exhibits strong interplay between charge density wave order and superconductivity. However, most of the results reported on this material come from theoretical calculations, preliminary bulk investigations and powder samples, which makes it difficult to uniquely determine the temperature evolution of its crystal structure and, consequently, of its charge density wave transition. Therefore, the published literature around LaPt2Si2 is often controversial. Here, by means of high-resolution synchrotron X-ray diffraction data, we clarify some of the poorly or partially understood aspects of the physics of LaPt2Si2. In particular, we resolve the complex evolution of its crystal structure and superstructures, identifying the temperature dependence of multiple density wave transitions in good quality LaPt2Si2 single crystals. According to our findings, on cooling from room temperature LaPt2Si2 undergoes a series of subtle structural transitions which can be summarised as follows: second order commensurate tetragonal (P4/nmm)-to-incommensurate structure followed by a first order incommensurate-to-commensurate orthorhombic (Pmmn) transition and then a first order commensurate orthorhombic (Pmmn)-to-commensurate tetragonal (P4/nmm). The structural transitions are accompanied by both incommensurate and commensurate superstructural distortions of the lattice. The observed behavior is compatible with discommensuration of the CDW in this material.

Evidence for a Pressure-Induced Phase Transition in the Highly Distorted TlNiO3 Nickelate

Rare-earth perovskite nickelates RNiO3 (R stands for Y, rare earths, Tl or Bi) have attracted wide attention in the past few decades because of their unique electronic properties that emerge from the insulator–metal transition (IMT). This transition can be tuned by chemical substitutions or by external variables, like pressure and temperature, but the mechanism of this transition still remains debated. While most previous studies focused on nickelates with partially filled 4f cations on the R site, here we studied the mechanism of the pressure-induced phase transition on a rare Tl3+ nickelate, which comprises fully filled 4f orbitals. We probed the pressure-induced structural and electronic changes taking place at the bulk, medium, and local atomic level at room temperature by using synchrotron X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) as probing techniques, respectively. High-resolution XRD data under ambient conditions show evidence for the monoclinic phase of TlNiO3, as characterized by the charge ordering between Ni3−δ and Ni3+δ in the insulator regime. High-pressure XRD data elucidated an anomaly in the evolution of the lattice parameters at 10.8 GPa, which we assigned to the structural transition P21/n → Pbnm. High-pressure EXAFS data at the Ni K-edge provide a solid proof for a short-order charge disproportionation under near ambient conditions. The Ni–O pair-bond compression curves unveiled an isotropic overlapping Ni t2g6eg1 → O 2p, with an anomaly at 10.8 GPa. The pressure evolution of the bond-distance variance (Debye–Waller exponents) lodged a hardening at this pressure point, suggesting constrained atomic displacements in the average range of ±0.04(5) Å. We propose that this reduced motional freedom could be linked to an electron–phonon coupling, which is the driving force behind the mechanisms of the IMT. We demonstrated that the XANES technique can be applied to ascertain the pressure-induced transition, by tracking the anomalous behavior of the position and width (full width at half-maximum) of the XANES features.

M6O4(OH)4 of M = Sn, Pb: Single Crystal Growth and Crystal Structure Determinations Far Away from Routine

Single crystals of Sn6O4(OH)4 have been grown over a period of more than a decade in hermetically sealed flasks of various triorganotin(IV)-trihydrides in toluene/N,N-dimethylformamide and those of Pb6O4(OH)4 on a petri dish within some days from the reaction of Pb(ClO4)2 with Sr(OH)2·8H2O. High-resolution X-ray diffraction data of the tetragonally crystallizing compounds have been collected conventionally at 100 K. Crystal structure determinations have been performed in space groups P4/mnc and P4¯21c with different structure models because of a pretended specific systematic extinction condition. Its violation was routinely overseen because of the very low intensities of the respective reflections, an effect reinforced by crystal size. The non-existence of this systematic extinction was experimentally confirmed by studying the datasets in more detail, including the simulation of layer photographs. The importance of additional information obtained from dataset analysis tools and structure validation programs to assess the different structure models is demonstrated. Structures of both molecules are analyzed with respect to the molecules as a whole as well as to their constructive building units: two crystallographic different prototypes of {MO4} coordination polyhedra with a bent seesaw conformation, one μ3-OH- and one μ3-O- group, each trigonal-pyramidally coordinated.

Crystal structure reinvestigation of silver(I) fluoride, AgF.

A crystal structure reinvestigation of AgF based on a low-temperature high-resolution single-crystal X-ray diffraction data is reported. Silver(I) fluoride crystallizes in the rock salt structure type (Fm m) with a unit-cell parameter of 4.92171 (14) Å at 100 K, resulting in an Ag-F bond length of 2.46085 (7) Å.

Synthesis of (μ2,η3-allyl-η5-oxapentadienyl)diiron pentacarbonyl complexes, an unusual reaction product from η4-(vinylketene)Fe(CO)3 complexes: structure and electron density distribution analysis.

The synthesis of a series of ferrocenylvinylketenes as stable η4-[Fe(CO)3] complexes (3a-f) was successfully accomplished through the reaction of η2-[Fe(CO)4] complexes under mild carbonylation conditions. The reactivity of 3a-f under thermal conditions afforded the unexpected formation of a novel family of (μ2,η3-allyl-η5-oxapentadienyl)diiron pentacarbonyl complexes 5a-f proposed to be formed by a sequence metathesis-haptotropic rearrangement between the starting η4-vinylketene iron(0) complex 3 and a η4-vinylcarbene iron(0) complex trapped in situ after a reversible carbonylation process favored by the thermal conditions. An electron density distribution analysis (EDD) of 5e using high-resolution X-ray diffraction data in combination with the DFT framework was performed to understand the electronic communication between the two iron fragments.

Investigation of C–F···F–C Interactions Using Experimental and Theoretical Charge Density Analyses

Among the halogens, fluorine plays a crucial role in governing the potency of drugs and pharmaceuticals. In this study, experimental and theoretical charge density analyses have been performed on N-(2,5-difluorophenyl)-3,5-difluoro-N-(3-methoxyphenethyl)benzamide to study the nature of weak intermolecular interactions, especially the F···F interactions, mediated by organic fluorine. The kind of C–F···F–C interactions analyzed in this study are Type I and quasi Type I/Type II. For this, the quantitative and qualitative analyses of electron densities have been performed based on the multipole modeling of high-resolution experimental X-ray diffraction data and theoretical structure factors generated from periodic calculations. The interactions have been analyzed based on the topological properties of electron densities using quantum theory of atoms in molecules (QTAIM). Thus, the nature of organic fluorine has been investigated by studying deformation of electron densities, Laplacian, and topological parameters.

Electron Density Analysis of Metal–Metal Bonding in a Ni4 Cluster Featuring Ferromagnetic Exchange

We present a combined experimental and theoretical study of the nature of the proposed metal-metal bonding in the tetranuclear cluster Ni4(NPtBu3)4, which features four nickel(I) centers engaged in strong ferromagnetic coupling. High-resolution single-crystal synchrotron X-ray diffraction data collected at 25 K provide an accurate geometrical structure and a multipole model electron density description. Topological analysis of the electron density in the Ni4N4 core using the quantum theory of atoms in molecules clearly identifies the bonding as an eight-membered ring of type [Ni-N-]4 without direct Ni-Ni bonding, and this result is generally corroborated by an analysis of the energy density distribution. In contrast, the calculated bond delocalization index of ∼0.6 between neighboring Ni atoms is larger than what has been found for other bridged metal-metal bonds and implies direct Ni-Ni bonding. Similar support for the presence of direct Ni-Ni bonding is found in the interacting quantum atom approach, an energy decomposition scheme, which suggests the presence of stabilizing Ni-Ni bonding interactions with an exchange-correlation energy contribution approximately 50% of that of the Ni-N interactions. Altogether, while the direct interactions between neighboring Ni centers are too weak and sterically constrained to bear the signature of a topological bond critical point, other continuous measures clearly indicate significant Ni-Ni bonding. These metal-metal bonding interactions likely mediate direct ferromagnetic exchange, giving rise to the high-spin ground state of the molecule.

Antisite disorder and Berry curvature driven anomalous Hall effect in the spin gapless semiconducting Mn2CoAl Heusler compound

Spin gapless semiconductors exhibit a finite band gap for one spin channel and a closed gap for another spin channel, and they have emerged as a new state of magnetic materials with a great potential for spintronic applications. The first experimental evidence for spin gapless semiconducting behavior was observed in an inverse Heusler compound ${\mathrm{Mn}}_{2}\mathrm{CoAl}$. Here, we report a detailed investigation of the crystal structure and anomalous Hall effect in ${\mathrm{Mn}}_{2}\mathrm{CoAl}$ using experimental and theoretical studies. The analysis of the high-resolution synchrotron x-ray diffraction data shows antisite disorder between Mn and Al atoms within the inverse Heusler structure. The temperature-dependent resistivity shows semiconducting behavior and follows Mooij's criteria for disordered metal. The scaling behavior of the anomalous Hall resistivity suggests that the anomalous Hall effect in ${\mathrm{Mn}}_{2}\mathrm{CoAl}$ is primarily governed by an intrinsic mechanism due to the Berry curvature in momentum space. The experimental intrinsic anomalous Hall conductivity (AHC) is found to be $\ensuremath{\sim}35$ S/cm, which is considerably larger than the theoretically predicted value for ordered ${\mathrm{Mn}}_{2}\mathrm{CoAl}$. Our first-principles calculations conclude that the antisite disorder between Mn and Al atoms enhances the Berry curvature and hence the value of intrinsic AHC, which is in very good agreement with the experiment.

Si Electrochemical Liquid Phase Epitaxy: Low-Temperature Growth of Hyperdoped Epitaxial Si Films

Epitaxial films of Si have been prepared at room temperature by electrochemical liquid phase epitaxy (ec-LPE). Crystalline Si films were grown on both Si(111) and Si(100) substrates, demonstrating clear evidence of low-temperature homoepitaxy. The ec-LPE method was demonstrated as a hybrid approach that combined elements of conventional electrodeposition and traditional liquid phase epitaxy. Voltammetric and amperometric data were collected that indicated conditions where Si ec-LPE is possible with SiCl4 in propylene carbonate electrolyte and eutectic gallium indium (e-GaIn) thin-film electrodes. Scanning electron micrographs, scanning transmission electron micrographs, and electron and X-ray diffraction data demonstrated that epitaxy extended throughout films that were several microns in thickness. Raman spectra, high-resolution X-ray diffraction data, time-of-flight secondary ion mass spectrometry, and energy-dispersive elemental mapping indicated that the as-prepared films were uniformly hyperdoped with Ga at >10 at %. These cumulative results demonstrate a distinct new way to realize crystalline Si films suitable for optoelectronic applications.

Quantitative x-ray diffraction analysis of strain and interdiffusion in β-Ga2O3 superlattices of μ-Fe2O3 and β-(AlxGa1−x)2O3

Superlattices composed of either monoclinic μ-Fe2O3 or β-(AlxGa1−x)2O3 with β-Ga2O3 spacers are grown on (010) β-Ga2O3 substrates using plasma-assisted molecular beam epitaxy. High-resolution x-ray diffraction data are quantitatively fit using commercial dynamical x-ray diffraction software (LEPTOS) to obtain layer thicknesses, strain, and compositions. The strain state of β-(AlxGa1−x)2O3 and μ-Fe2O3 superlattices as characterized using reciprocal space maps in the symmetric (020) and asymmetric (420) diffraction conditions indicates coherent growths that are strained to the (010) β-Ga2O3 lattice. β-(AlxGa1−x)2O3 and μ-Fe2O3 superlattices grown at hotter substrate temperatures result in crystal structures with better coherency and reduced defects compared to colder growths. The growth rate of μ-Fe2O3 is ∼2.6 nm/min at Tsub = 700 °C and drops to ∼1.6 nm/min at Tsub = 800 °C due to increased Fe interdiffusion at hotter substrate temperatures. Scanning transmission electron microscopy data of a μ-Fe2O3 superlattice grown at Tsub = 700 °C confirm that there is significant diffusion of Fe atoms into β-Ga2O3 layers.

Electrical and Structural Properties of Two-Inch Diameter (0001) α-Ga2O3 Films Doped with Sn and Grown by Halide Epitaxy

Two-inch diameter α-Ga2O3 films with thickness ∼4 μm were grown on basal plane sapphire by Halide Vapor Phase Epitaxy (HVPE) and doped with Sn in the top ∼1 μm from the surface. These films were characterized with High-Resolution X-ray Diffraction (HRXRD), Scanning Electron Microscope (SEM) imaging in the Secondary Electron (SE) and Micro-cathodoluminescence (MCL) modes, contactless sheet resistivity mapping, capacitance-voltage, current-voltage, admittance spectra, and Deep Level Transient Spectroscopy (DLTS) measurements. The edge and screw dislocations densities estimated from HRXRD data were respectively 7.4 × 109 cm−2 and 1.5 × 107 cm−2, while the films had a smooth surface with a low density (∼103 cm−2) of circular openings with diameters between 10 and 100 μm. The sheet resistivity of the films varied over the entire 2-inch diameter from 200 to 500 Ω square−1. The net donor concentration was ∼1018 cm−3 near the surface and increased to ∼4 × 1018 cm−3 deeper inside the sample. The deep traps observed in admittance and DLTS spectra had levels at Ec−0.25 eV and Ec−0.35 eV, with concentration ∼1015 cm−3 and Ec−1 eV with concentration ∼1016 cm−3.

Self-Activating Strontium Orthoborate Blue Phosphors Induced by Cation and Anion Deficiencies and Their Rare-Earth-Free White Ultraviolet Light-Emitting Diodes.

Self-activating blue-light-emitting strontium orthoborate phosphors, viz., Sr3B2+xO6+3x/2 and Sr3B2+xO6+3x/2-δ (x ranges from -0.3 to 0.1), were obtained by varying the number of BO3/2 and anion deficiencies. The integrated intensity observed from the oxygen 1s profile obtained via X-ray photoelectron spectroscopy indicated the relative concentrations of the oxygen vacancies in the Sr3B2+xO6+3x/2 (x = 0, -0.1, and -0.3) and Sr3B2O6-δ phosphors. The structures of Sr3B2O6, Sr3B2.1O6.15, Sr3B1.9O5.85, and Sr3B2O6-δ with crystal orientations were analyzed based on high-resolution synchrotron powder X-ray diffraction data. A mixture of rare-earth-free blue Sr3B2O6-δ and yellow Sr2.45Ba0.5Na0.05Al0.95Sn0.05O4-αF1-δ phosphors, incorporated on a 315 nm UV-LED chip, can generate a white-light UV-LED.

Path Less Traveled: A Contemporary Twist on Synthesis and Traditional Structure Solution of Metastable LiNi12B8.

Achieving kinetic control to synthesize metastable compounds is a challenging task, especially in solid-state reactions where the diffusion is slow. Another challenge is the unambiguous crystal structure determination for metastable compounds when high-quality single crystals suitable for single-crystal X-ray diffraction are inaccessible. In this work, we report an unconventional means of synthesis and an effective strategy to solve the crystal structure of an unprecedented metastable compound LiNi12B8. This compound can only be produced upon heating a metastable layered boride, HT-Li0.4NiB (HT: high temperature), in a sealed niobium container. A conventional heating and annealing of elements do not yield the title compound, which is consistent with the metastable nature of LiNi12B8. The process to crystallize this compound is sensitive to the annealing temperature and dwelling time, a testament to the complex kinetics involved in the formation of the product. The unavailability of crystals suitable for single-crystal X-ray diffraction experiments prompted solving the crystal structure from high-resolution synchrotron powder X-ray diffraction data. This compound crystallizes in a new structure type with space group I4/mmm (a = 10.55673(9) Å, c = 10.00982(8) Å, V = 1115.54(3) Å3, Z = 6). The resulting complex crystal structure of LiNi12B8 is confirmed by scanning transmission electron microscopy and solid-state 11B and 7Li NMR spectroscopy analyses. The extended Ni framework with Li/Ni disorder in its crystal structure resulted in the spin-glass or cluster glass type magnetic ordering below 24 K. This report illustrates a “contemporary twist” to traditional methodologies toward synthesizing a metastable compound and provides a recipe for solving structures by combining the complementary characterization techniques in the cases where the traditionally used single-crystal X-ray diffraction method is nonapplicable.

New acylglycosides from the roots of Rheum palmatum L.

A phytochemical investigation of the EtOH extract of the roots of Rheum palmatum L. was performed, leading to the isolation of 3 new acylglycosides ( 1 – 3 ) and 19 previously reported compounds, including 4 cinnamoyl glucosides ( 4 – 7 ) and 15 anthraquinones ( 8 – 22 ). Their structures were elucidated using nuclear magnetic resonance, infrared, ultraviolet and high-resolution electrospray ionization mass spectra and X-ray diffraction data. The biological activities of compounds 2 , 4 – 9 , and 11 – 13 , including their lymphocyte activation gene 3 (LAG3)/major histocompatibility complex class II (MHC II) and LAG3/fibrinogen-like protein 1 (FGL1) binding inhibition activities, were evaluated. Among the isolates, compound 7 exhibited clear inhibitory activity against the LAG3/FGL1 interaction with an IC 50 of 7.89 μ M, meanwhile compound 6 inhibited the LAG3/MHC II interaction with an IC 50 of 6.00 μ M. • Three undescribed acylglycosides were isolated from roots of Rheum palmatum L. • The absolute configuration of 1 was confirmed by single crystal X-ray diffraction. • This is the first report of the crystal structure of a cinnamoyl glucoside. • Their activities against the interaction of LAG3 with MHC II or FGL1 were evaluated.

放射光X線単結晶X線回折による価電子密度分布解析

The valence electron density distribution in crystals can be observed with high accuracy by precise electron density analysis using the core differential Fourier synthesis （CDFS） method with high-intensity and high-resolution single crystal X-ray diffraction data obtained at a large synchrotron radiation facility; SPring-8. By observing the spatial distribution of electron density proportional to the square of the wave function, the quantum parameters of the orbital states of can be directly determined. Using this method, not only orbital ordered states and bonding electrons but also degenerate orbital states can be directly observed, which may lead to a new method for structural properties research beyond the conventional structural analysis.