Powder Diffraction Research Articles

Enhanced Dissolution and Antibacterial Potential of Cinacalcet Hydrochloride via Ternary Solid Dispersions

Cinacalcet hydrochloride (HCl), a calcium-sensing receptor agonist used to treat hyperparathyroidism, suffers from poor solubility, reducing its bioavailability. Recently, cinacalcet HCl has been probed for repurposing as antibacterial agent. This work investigates cinacalcet HCl's potential as an antibacterial agent and provides a formulation to improve the drug dissolution. Solid dispersion formulations using Poloxamer 407, with and without Soluplus®, were prepared via solvent evaporation and hot melt congealing methods. The resulting formulations were analyzed using differential scanning calorimetry, FTIR spectroscopy, X-ray powder diffraction, and dissolution studies. These formulations significantly enhanced cinacalcet HCl dissolution compared to the unprocessed form, achieving up to a 15-fold increase in Q5 (percent of cinacalcet HCl dissolved after 5 minutes). The dissolution efficiency rose from 28% for the pure drug to 94.8% and 87.8% for formulations F6 and F7, respectively. Microbiological evaluations confirmed the antibacterial effect of cinacalcet HCl, which was notably increased in the Poloxamer 407 and Soluplus® hybrid formulation (F7) with a MIC of 64-128 µg/ml. Antibiofilm activity was also observed, with qRT-PCR indicating downregulation of biofilm genes (icaA, icaD, and fnbA). This study introduces a cinacalcet HCl formulation prepared using a scalable, green approach, demonstrating significant potential for antimicrobial applications.

Influence of the Carboxylates in the 3D Pb(II) Based Catalysts on the Electrochemical Oxygen Evolution Reaction.

The Oxygen Evolution Reaction (OER) is considered to be one of the important processes for energy storage and conversion applications. However, due to its sluggish kinetics it becomes extremely crucial to design and develop cost-effective, stable and highly efficient electrocatalysts. Herein, we report two lead(II)based coordination polymers (CPs) {[Pb2(TPBN)(TDC)2].2H2O}n (CP1), and {[Pb2(TPBN)(FDC)2]}n (CP2) synthesized via self-assembly at ambient conditions in good yields (where TPBN= N,N',N‴,N‴'-tetrakis-(2-pyridylmethyl)-1,4-diaminobutane, H2TDC= 2,5-2,5-thiophenedicarboxylic acid, and H2FDC = 2,5-furandicarboxylic acid. Their 3D structures were determined by Single-crystal X-ray diffraction (SCXRD) studies. The bulk purity and thermal stability of CP1 and CP2 were studied by powder X-ray diffraction studies and thermogravimetric analysis, respectively. Both the CPs showed remarkable catalytic activity for the OER. With a current density of 15 mAcm-2, for both CP1 and CP2, overpotentials of 570 mV and 630 mV with tafel slope values of 112 mV dec-1, and 178 mV dec-1 respectively for CP1 and CP2 in 1.0 M alkaline (KOH) solution was obtained. It is notable that the difference in their catalytic performance - CP1 is better than CP2, can be attributed to the subtle single heteroatom in the dicarboxylate ring (S in thiophene and O in furan, respectively).

Effect of pH and Buffer Capacity of Physiological Bicarbonate Buffer on Precipitation of Drugs.

The purpose of this study was to investigate the effect of the pH and buffer capacity (β) of physiological bicarbonate buffer solutions (BCB) on drug precipitation. The precipitation profiles of poorly soluble drugs in BCB were evaluated by using a pH-shift precipitation test. Phosphate buffer solutions (PPB) were used for comparison. Two weakly acidic drugs (pKa: 4.9 and 7.0) and two weakly basic drugs (pKa: 6.1 and 8.3) were used as model drugs. The bulk phase pH value (pHbulk) and β values were set to cover the physiological range in the small intestines (pH: 5.5 to 7.5, β: 2.2 to 17.6 mM/ΔpH). A floating lid was used to maintain the pHbulk of BCB to avoid CO2 loss. It was also applied to PPB to align the experimental conditions. Each drug was completely dissolved in HCl (pH 3.0, for weakly basic drugs) or NaOH (pH 11.0, for weakly acidic drugs) solutions (450 mL, 50 rpm, 37 °C). The pHbulk value was then shifted to the neutral pH region by adding a 10-fold concentrated buffer solution (50 mL, final volume of 500 mL). The initial total drug concentration (neutral + ionized species) was set so that the concentration and supersaturation ratio of the neutral species were the same under all pHbulk conditions. The solid forms of the precipitates were determined by powder X-ray diffraction and differential scanning calorimetry. In BCB, as pHbulk was increased above (for weakly acidic drugs) or decreased below (for weakly basic drugs) the drug pKa value, the precipitation of the free form solid became slower. As β was increased, drug precipitation in BCB became faster. Drug precipitation in PPB was faster than that in BCB and less affected by pHbulk and β. In BCB, at pHbulk at which a drug is ionizable, the surface pH of the precipitating particles can differ from pHbulk because of the slow hydration process of CO2. In conclusion, pHbulk and β affected the precipitation of weakly acidic and basic drugs in BCB. As BCB is a physiological buffer in the small intestine, it should be used for precipitation studies of weakly acidic and basic drugs.

Design and evaluation of multicomponent systems as a potential strategy to enhance the pharmaceutical performance of albendazole desmotropes.

Albendazole, an anthelmintic recognized by the World Health Organization as an essential medicine, is known to have limitations in solubility and bioavailability. To improve these properties, binary and ternary multicomponent systems were designed employing different combinations of albendazole desmotropes with maltodextrin and aspartic acid. The impact of these systems in solution was evaluated through phase solubility analysis. Moreover, solid systems were produced using the kneading method and evaluated with a combination of techniques, including dissolution tests, Fourier-Transform infrared spectroscopy, X-ray powder diffraction, and scanning electron microscopy. These studies demonstrated that multicomponent systems had higher solubility than free desmotropes, with the system formulated using solid form II of albendazole exhibiting the most significant improvement. Additionally, the dissolution percentage of each solid system in simulated gastric fluid was significantly increased. It can therefore be concluded that these innovative systems offer promising alternatives for improving the oral bioavailability of albendazole, generating significant interest in the pharmaceutical field.

Mineralogical Characteristics and Color Origin of Nephrite Containing Pink Minerals

Recently, a variety of nephrite containing localized pink mineral aggregates has emerged on the market, which is sometimes referred to as “peach blossom jade” by some merchants. Currently, there is limited research on this type of nephrite containing pink minerals, and its detailed mineral composition characteristics and coloration mechanisms remain unclear. In this study, four samples of nephrite containing pink minerals were systematically investigated using conventional gemological tests, as well as modern analytical techniques such as X-ray powder diffraction (XRD), infrared spectroscopy (IR), laser Raman spectroscopy, ultraviolet–visible (UV-Vis) absorption spectroscopy, electron probe microanalysis (EPMA), and X-ray fluorescence spectroscopy (XRF). These techniques were employed to elucidate the mineral composition, chemical composition, spectroscopic features, and coloration origins of the samples. The results indicate that the primary mineral constituent of the samples is tremolite, with accessory minerals including zoisite, muscovite, orthoclase, andesine, diopside, and prehnite. The major chemical components of the samples are SiO2, CaO, and MgO, along with minor amounts of Al2O3, K2O, and FeOT. The overall green hue of the samples is positively correlated with Fe content. The pink mineral present in the samples is predominantly Mn-bearing zoisite, and the pink coloration of zoisite is primarily attributed to the energy level transitions of Mn2+ at approximately 540 nm and 440 nm.

An extended thermal pressure equation of state for sodium fluoride

The effect of pressure and temperature on the unit-cell volume of NaF has been measured by X-ray powder diffraction at ambient pressure between 12 and 300 K and neutron powder diffraction up to 5 GPa between 140 and 350 K. These data have been combined with high-pressure volume data at 300 and 950 K to 25 GPa and adiabatic bulk modulus data to 650 K to define an equation of state for NaF relating molar volume to both temperature and pressure. The model combines a fourth-order Birch–Murnaghan equation of state at 295 K with a Mie–Grüneisen–Debye model for thermal pressure. The parameters of the model set at 295 K and ambient pressure are as follows: reference unit-cell volume V 0 = 14.9724 (5) cm3 mol−1, isothermal bulk modulus K 0T = 46.79 (14) GPa, first derivative of the bulk modulus K′0T = 5.72 (12), second derivative of the bulk modulus K′′0T = −0.43 (4) GPa−1, Debye temperature T MGD = 459 (3) K, and Anderson Grüneisen parameters γ0 = 1.547 (11) and q = 0.94 (18).

Thermal diffuse scattering analysis of Ag2O binary system via X-ray powder diffraction

Diffuse scattering is a component of the powder pattern bearing information on the local atomic structure and disorder of crystalline materials. It is visible in the X-ray diffraction patterns of binary structures like Ag2O, which has a large mean squared displacement for its constituent elements. Pair distribution function (PDF) analysis is widely employed to extract this local structural information, embedded in the widths of PDF peaks. However, obtaining the PDF from experimental data requires a Fourier transform, which introduces aberrations in the transformed data due to instrument resolution, complicating the distinction between its static and dynamic components. In this work, the analysis of thermal diffuse scattering is performed directly on the X-ray powder pattern, using the traditional Rietveld method integrated with a correlated displacement model for atomic pairs. The Ag2O case study data were collected using synchrotron radiation at room temperature, supplemented by laboratory experiments up to 200°C. An Einstein model was used to obtain the harmonic and anharmonic force constants of the system. The force constants were also obtained via density functional theory and ab initio molecular dynamics simulations and showed similar values to the experiments. The analysis reveals the complex dynamic structure of Ag2O, characterized by high anisotropy in phonon dispersion relations and the presence of soft phonon modes, which explain the significant displacement parameters observed. The proposed approach can be easily employed for other binary or more complex systems to understand the dynamics of local forces through X-ray diffraction analysis.

Molybdenum disulfide nanosheets hybridized with lysine molecules for highly efficient near-infrared photothermal energy conversion

The paper reports a facile way for noncovalent functionalization of 1T-MoS2 with L-lysine (Lys) monolayers. The structure of the resultant hybrid compound was revealed by the powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, absorption spectroscopy and density functional theory (DFT) calculations study. A significant strength of the in-layer organic and organic-inorganic hydrogen bonding amounting to 24.6 and 29.9 kcal per mole of Lys, respectively, was found to hold the hydrated Lys molecules arranged in 2D chains and keep these chains tightly bound to the MoS2 sheets. The MoS2 hybridization with Lys significantly rises the upper temperature stability limit of 1T-MoS2 polymorph, which possesses the remarkable photothermal properties in near infra-red (NIR) region. The hybrid structure demonstrates excellent photothermal light-to-heat conversion efficiency reaching 49.5% upon 808 nm laser irradiation and higher thermal durability than unmodified 1T-MoS2.

Catalytic-assisted remediation and phytotoxicity evaluations of organic pollutants in the presence of metal-doped Bi2O3-based NPs catalyst.

The chemical co-precipitation method was used to synthesize a variety of pure Bi2O3 and substituted Bi2-2xCoxCdxO3 NPs (x=0.0-0.8) and doping influences were evaluated based on the optical, photocatalytic, morphological, and structural characteristics. Powder X-ray diffraction (PXRD), scanning electron microscope (SEM), Energy dispersive X-ray (EDX), Fourier-transform infrared spectroscopy (FTIR), and UV-visible techniques were used to explore the characteristics of the synthesized Bi2O3-based NPs. XRD measurements confirmed the monoclinic structure and a P21/c space group, whereas the particle size was between 22 and 41nm. The SEM analysis gives the morphology of the synthesized NPs that were diverse and agglomerated platelets, whereas the EDX measurements provide the presence of Co and Cd in Bi2-2xCoxCdxO3 NPs. Additionally, FTIR investigations confirmed the existence of functional groups in Bi2-2xCoxCdxO3 NPs. The ultraviolet-visible absorbance region displaying a considerable red shift allowed for tuning of the band gap from 2.64 to 2.37eV. By analyzing the degradation of Reactive Black 5 (RB-5) dye in the presence of sunlight, pure Bi2O3 NPs showed 65.04% whereas the substituted Bi2-2xCoxCdxO3 NPs demonstrated enhanced photodegradation (86.40%) in 105min. For the degradation of RB-5 dye, the effects of catalyst dosage, dye concentration, and pH variations were studied as well. The phytotoxicity experiment was also performed by comparing the germination of Triticum aestivum seeds in treated and untreated RB-5 dye. In the untreated dye solution, seed germination was 50% inhibited, and in the treated dye solution, germination was observed to be 80%. Additionally, recycling investigations were used to confirm the stability of these fabricated nanoparticles, and the results showed that nanomaterials exhibited significant stability and reusability. Co and Cd-doped Bi2O3 NPs are promising solar-active photocatalysts for dye removal from wastewater applications because of their improved photocatalytic activity and narrow bandgap.

Synthesis and Characterization of K2Ba3(P2O7)2:VO2+ Nanopowder: Reddish-Orange Emission for LED Applications.

Solid-state reaction method is employed to prepare K2Ba3(P2O7)2:VO2+ nanopowder and studied by using powder x-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, optical absorption spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and photoluminescence (PL) spectroscopy. XRD studies revealed VO2+ ion doped K2Ba3(P2O7)2 nanopowder have 21 nm crystallite size, orthorhombic phase, and Pmn21 space group. From Williamson-Hall analysis, crystallite size is found as 24 nm. SEM morphology recorded the presence of irregular-sized and round-shaped agglomerates. FT-IR and Raman spectra reveal characteristic bands of phosphate groups. Three characteristic peaks are observed at 848, 695, and 452 nm in optical absorption spectrum. Also, crystal and tetragonal field parameters are calculated as Dq = 1439, Ds = -2789, and Dt = 3422 cm-1. In addition, bandgap energy is found as 3.97 eV. Optical and EPR analyses led to understand the incorporation of vanadyl ions into host lattice. Spin Hamiltonian parameters are evaluated. Basing PL spectrum, Commission Internationale de l'Éclairage's (CIE) chromaticity coordinates are calculated, which are present in reddish-orange region with good color correlated temperature (CCT) and color rendering index (CRI) values facilitating the use in lighting applications and LEDs.

In vitro and in vivo characterization of Invega Sustenna® (paliperidone palmitate long-acting injectable suspension).

The aim of this study was to comprehensively characterize paliperidone palmitate (PP) long-acting suspension (Invega Sustenna®) through reverse engineering. We developed a series of analytical methods to assess critical quality attributes of four batches of Invega Sustenna®. The size distributions of the four batches of suspensions were measured using laser diffraction, and variations in the D50 and D90 parameters were observed. The morphology of suspension was determined through scanning electron microscope (SEM), which exhibited irregular granular shape across all batches. The size distributions determined by SEM images were similar to the laser diffraction results. Thermal characteristics were detected using differential scanning calorimetry (DSC) and crystalline properties were assessed by powder X-ray diffraction (PXRD), displaying consistency among the four batches in these two aspects. In vitro dissolution methods (sample separation and dialysis bag methods) were developed to evaluate the release behaviors of Invega Sustenna® and four lots showed a similar dissolution pattern. Furthermore, following a single-dose intramuscular administration to rats, two batches of Invega Sustenna® with the largest size differences demonstrated comparable plasma concentration-time profiles and pharmacokinetics parameters, indicative of one month long-acting release. In summary, we established a systematic quality characteristics assessment for Invega Sustenna®, including particle size distribution, particle morphology, thermal characteristics, crystalline properties, in vitro dissolution kinetics and in vivo pharmacokinetics. Our work will assist pharmaceutical companies and regulatory agencies in the development and regulatory assessment of novel or generic products of long-acting injectable suspension.

Application of signal separation to diffraction image compression and serial crystallography

We present here a methodology for real-time analysis of diffraction images acquired at a high frame rate (925 Hz) and its application to macromolecular serial crystallography at ESRF. We introduce a new signal-separation algorithm, able to distinguish the amorphous (or powder diffraction) component from the diffraction signal originating from single crystals. It relies on the ability to work efficiently in azimuthal space and is implemented in pyFAI, the fast azimuthal integration library. Two applications are built upon this separation algorithm: a lossy compression algorithm and a peak-picking algorithm. The performances of both are assessed by comparing data quality after reduction with XDS and CrystFEL.

Characterization and calibration of DECTRIS PILATUS3 X CdTe 2M high-Z hybrid pixel detector for high-precision powder diffraction measurements

Silicon-based hybrid photon-counting pixel detectors have become the standard for diffraction experiments of all types at low and moderate X-ray energies. More recently, hybrid pixel detectors with high-Z materials have become available, opening up the benefits of this technology for high-energy diffraction experiments. However, detection layers made of high-Z materials are less perfect than those made of silicon, so care must be taken to correct the data in order to remove systematic errors in detector response introduced by inhomogeneities in the detection layer, in addition to the variation of the response of the electronics. In this paper we discuss the steps necessary to obtain the best-quality powder diffraction data from these detectors, and demonstrate that these data are significantly superior to those acquired with other high-energy detector technologies.

Tutorial review on catalyst characterization and materials preparation for x-ray powder diffraction analysis

Tutorial review on catalyst characterization and materials preparation for x-ray powder diffraction analysis

ASUGNN: an asymmetric-unit-based graph neural network for crystal property prediction

Material properties can often be derived directly from fundamental equations governing electron behavior. In this study, we present an open-source asymmetric-unit-based graph neural network designed to capture atomic patterns and their corresponding electron distributions. By coarse-graining sites belonging to conjugate subgroups and analyzing reciprocal space through powder X-ray diffraction patterns, our model predicts key physical properties, including formation energy, band gap, bulk modulus and metal/non-metal classification. Our method demonstrates exceptional predictive accuracy for properties calculated using density functional theory across the Materials Project dataset. Our approach is compared with state-of-the-art models and exhibits impressively low error rates in zero-shot predictions.

A new coamorphous ethionamide with enhanced solubility: Preparation, characterization, in silico pharmacokinetics, and controlled release by encapsulation.

This study reports the synthesis and the experimental-theoretical characterization of a new coamorphous system consisting of ethionamide (ETH) and mandelic acid (MND) as a coformer. The solid dispersion was synthesized using the slow solvent evaporation method in an ethanolic medium. The structural, vibrational, and thermal properties of the system were characterized. Density functional theory (DFT) calculations were performed to analyze the interactions between ETH and MND in the heterodimer. These results contributed to the suitable assignment of infrared (IR) vibrational modes, to determine the chemical reactivity descriptors and the electronic indices of each component of the molecule. Additionally, Hirshfeld surfaces analysis and calculations of absorption, distribution, metabolism, and excretion (ADME) parameters were performed to examine intermolecular interactions and predict the in silico pharmacokinetic profile of the ETH-MND compound and its forming molecules. Powder X-ray diffraction data confirmed the formation of a coamorphous binary system in the 1:2 and 1:3 ETH and MND ratios. Furthermore, the ETH-MND (1:3) solid dispersion remained amorphous for up to 150days when stored at 38°C and 75% relative humidity. DFT calculations, conducted both in vacuum and in ethanol, indicated that the formation of the coamorphous system is driven by hydrogen bonding between the NH2 groups of ETH and the C=O group of MND. Thermodynamic analysis showed that intermolecular interactions are favored in the gas phase, with Gibbs free energy of -3.20kcal/mol. The IR spectra showed a correlation between experimental and calculated data. Thermal analyses revealed glass transition temperatures of 59°C (1:2 ratio) and 61°C (1:3 ratio), indicating thermal stability of the coamorphous materials. Additionally, dissolution tests showed a 3.58-fold increase in the solubility of ETH compared to its crystalline form. The encapsulation of ETH-MND coamorphous systems in sodium alginate spheres via polyelectrolyte complexation was also investigated, demonstrating significant controlled drug release over 480min.

Crystallography of the litharge to massicot phase transformation from neutron powder diffraction data.

The crystallographic phase change from tetragonal litharge (α-PbO; P4/nmm) to orthorhombic massicot (β-PbO; Pbcm) has been studied by full-matrix Rietveld analysis of high-temperature neutron powder diffraction data collected in equal steps from ambient temperature up to 925 K and back down to 350 K. The phase transformation takes place between 850 and 925 K, with the coexisting phases having equal abundance by weight at 885 K. The product massicot remains metastable on cooling to near ambient temperature. Both structures are layered networks of OPb4 tetrahedra and PbO4 square pyramids, with the space between alternate layers of Pb atoms (in approximate cubic close packing) occupied either by O atom layers or Pb atom lone pairs. In massicot, the symmetric Pb and O layers of litharge become deeply corrugated parallel to [001], with the O-atom layers splitting into two layers, although these are still sandwiched between the approximately cubic close-packed Pb atom layers. The crystallite size of the initial litharge component decreases from around 3500 Å to around 1100 Å at the midpoint of the phase change at 885 K, whereupon the size of the massicot crystallites increases from a similar value to around 2500 Å at 350 K during the cool-down stage. The unit-cell dimensions and atomic coordinates of litharge change smoothly throughout the phase change, but there is a rapid expansion of the c-axis immediately prior to the recrystallization to massicot, and the one free coordinate (Pb z) decreases significantly to producer a thinning of the layers. Increases in the O displacment parameters suggest that this atom is `on the move' as the transformation approaches. Changes in the massicot parameters as its crystallites emerge from the transformation are largely unremarkable. The formation of the heavily corrugated layers in massicot requires significant movements of the O atoms (∼1.2 Å) from their positions in litharge and thus for Pb-O bonds to be broken during the phase change. The requirement for these bonds to be re-broken in a conversion back to litharge is likely to be the reason why massicot is metastable at ambient temperature. Evidence of a temporary intermediate `amorphous' phase in the phase transformation from which the massicot grows is provided in the form of broad, very low amplitude `peaks' in the high-temperature diffraction patterns.

Modulation of the modulated magnetic structure of an Ho i-MAX phase described by a magnetic (3+2)-dimensional superspace group.

The magnetic structures of the Ho-based i-MAX phase (Mo2/3Ho1/3)2GaC were studied with neutron powder diffraction at low temperature. (Mo2/3Ho1/3)2GaC crystallizes in the orthorhombic space group Cmcm. The material undergoes two successive antiferromagnetic transitions at TN1 = 10 K and TN2 = 7.2 K. The magnetic structure below TN1 is incommensurate with the propagation vector k1= (0, ky, 0) with ky = 0.696 (1) at 9 K. For the analysis of the magnetic structure, a group-theoretical approach based on the space group of the nuclear structure and its subgroups was employed. A model in the (3+1)D superspace group Cmcm.1'(0β0)s0ss yielded the most accurate results in neutron powder diffraction refinements. The determined structure was found to be an incommensurate longitudinal amplitude-modulated magnetic structure. Below TN2, additional magnetic satellites develop. They could be indexed by a propagation vector k2 = (τx, 0, 0) with the τx value increasing below TN2 until it stabilizes at approximately 3 K at 0.075. A magnetic structure determination considering two propagation vectors k1 and k2 was carried out using the superspace formalism by building the corresponding (3+2)D model. The determination was based on the observation that the additional magnetic peaks emerge exclusively in the vicinity of the incommensurate magnetic peaks with propagation vector k1, and not in the vicinity of nuclear peaks. This indicates that only mixed-index reflections were observed, and not reflections purely related to k2. The magnetic superspace group (MSSG) that was determined is Amma.1' (0,β,0)00s0 (0,0,γ)ss0s. The structure can be described as a longitudinal amplitude-modulated structure, which itself is amplitude-modulated in a perpendicular direction. This represents a very unusual case of a 2-k magnetic structure with no symmetry relation between the propagation vectors.

Diamagnetic, binary Sulfide Ba3Sc2S6 – with Infinite [ScS6/2] Chains as structural Element

The ternary sulfide, Ba3Sc2S6, was synthesized by the conventional high-temperature solid-state technique in an inert atmosphere, utilizing sealed silica ampules with low internal pressure of Ar gas. The crystal structure was determined by single crystal X-ray diffraction and can be described by a trigonal crystal lattice with rhombohedral symmetry, Rc (No. 167), with powder diffraction unit cell parameters a = 12.0402(1) Å and c = 13.3893(2) Å. The compound crystallizes with the K4CdCl6-type structure, which has been used to describe homologous sulfides. This crystal structure shares features with the 2H perovskites but contains infinite 1D chains, Niggli notation , consisting of alternating, distorted octahedra and trigonal prisms connected by face-sharing. Ba3Sc2S6 is diamagnetic, as determined from magnetic susceptibility measurements. UV-Vis spectroscopy data suggest a direct bandgap of about 2.9 eV. Further, DFT calculations reveal a band gap of about 1.8 eV and 2.9 eV using the PBE and the HSE06 functional, respectively, of which the latter agrees perfectly with UV-Vis observations.

Molecular Network Polyamorphism in Mechanically Activated Arsenic Selenides Under Deviation from As2Se3 Stoichiometry

Polyamorphic transitions driven by high-energy mechanical milling (nanomilling) are studied in thioarsenide As4Sen-type glassy alloys obtained by melt quenching deviated from arsenic triselenide As2Se3 stoichiometry towards tetraarsenic pentaselenide (g-As4Se5) and tetraarsenic tetraselenide (g-As4Se4). This employs a multiexperimental approach based on powder X-ray diffraction (XRD) analysis complemented by thermophysical heat transfer, micro-Raman scattering (micro-RS) spectroscopy, and revised positron annihilation lifetime (PAL) analysis. Microstructure scenarios of these nanomilling-driven transformations in arsenoselenides are identified by quantum-chemical modeling using the authorized modeling code CINCA (the Cation Interlinked Network Cluster Approach). A straightforward interpretation of a medium-range structure response of a nanomilling-driven polyamorphism in the arsenoselenides is developed within the modified microcrystalline model. Within this model, the diffuse peak-halos arrangement in the XRD patterning is treated as a superposition of the Bragg-diffraction contribution from inter-planar correlations supplemented by the Ehrenfest-diffraction contribution from inter-atomic (inter-molecular) correlations related to derivatives of network As2Se3-type and molecular As4Se4 -type conformations. Changes in the medium-range structure of examined glassy arsenoselenides subjected to nanomilling occur as an interplay between disrupted intermediate-range ordering and enhanced extended-range ordering. The domination of network-forming conformations in arsenoselenides deviated from As2Se3 stoichiometry (such as g-As4Se5) results in rather slight changes in their calorimetric heat-transfer and micro-RS responses. At the atomic-deficient level probed by PAL spectroscopy, these changes are accompanied by reduced positron trapping rate of agglomerated multiatomic vacancies and vacancy-type clusters in an amorphous As-Se network. Under an increase in As content beyond the g-As4Se5 composition approaching g-As4Se4, nanomilling-driven polyamorphic transitions, which can be classified as reamorphization (amorphous I-to-amorphous II) phase transitions, are essentially enhanced due to the higher molecularity of these glassy alloys enriched in thioarsenide-type As4Se4 cage-like molecular entities and their low-order network-forming derivatives.