Site Occupancy Research Articles

An iron‐based fluorophosphate cathode material for K‐ion batteries

The development of a tavorite structured K‐ transition metal (TM)‐ fluorophosphate, having earth‐abundant Fe as the only TM, crystallizing in the orthorhombic crystal system and facilitating stable‐cum‐reversible electrochemical K‐extraction/insertion, has been reported here. Synthesized using low‐cost precursors, KFePO4F has also been found to be air‐stable. Detailed information pertaining to the bonding/structure, including lattice site occupancy, have been obtained via diffraction, Raman spectroscopy and FTIR, with XPS and ESR revealing the oxidation states of Fe in the as‐synthesized condition and upon being subjected to electrochemical potassiation/depotassiation. The electrochemical K‐insertion/extraction, supported by reversible Fe‐redox, leads to a reversible K‐storage capacity of ~102 mAh/g (within 1.5‐4.0 V), along with a 1st cycle Coulombic efficiency (CE) of ~93% (with CE >99.9% from 2nd cycle). Ex‐situ X‐ray diffraction, as well as operando synchrotron diffraction during galvanostatic cycling, indicates reversible changes in peak positions upon electrochemical K‐extraction/insertion, with no evidence for structural change. When used as cathode material in K‐ion ‘full’ cell (with hard carbon‐based anode), a discharge capacity of ~68 mAh/g, along with capacity retention of ~70% after 50 cycles, has been obtained; which confirms that this newly‐developed earth‐abundant Fe‐based potassium fluorophosphate can be utilized for potential application in sustainable battery chemistries, like K‐ion batteries.

2-Amino-5-oxo-4-(thiophen-2-yl)-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile

The crystal structure of the title compound, C14H12N2O2S, reveals two symmetrically independent molecules within the asymmetric unit. Each molecule contains a chromenone core attached to a 2-thiophene ring, cyano, and amino groups. The 2-thiophene ring of one of the two molecules in the asymmetric unit was found to be disordered over two positions, with the major component having a site occupancy factor of 0.837 (2). The 2-thiophene ring is nearly orthogonal to the fused 4H-pyran ring, with dihedral angles between the two sets of planes being 89.5 (5) and 89.63 (8)°. Intermolecular hydrogen bonding, involving N—H...N and N—H...O interactions, creates two distinct motifs leading to the formation of a two-dimensional supramolecular network along the crystallographic ac plane.

Open Sn Framework Structure Hosting Bi Guest atoms – Synthesis, Crystal and Electronic Structure of Na13Sn26Bi

Although several Na‐Sn‐Pnictides with a variety of structural motives are known, no ternary compound in the Na‐Sn‐Bi system has been described yet. In this paper we present the Zintl‐phase Na13Sn25.73Bi1.27 comprising a complex, open‐framework structure of Sn atoms, with one mixed Sn/Bi site, hosting Na atoms. An additional Bi atom is loosely connected with only weak contacts to the framework filling a larger cavity within the network. According to band structure calculations of the two ordered variants with either full occupation of the mixed site with Sn or Bi, resulting in Na13Sn26Bi and Na13Sn24Bi3, respectively, both compounds are semiconductors with band gaps of 0.5 eV. A comparison of the band structures with the related binary compounds Na5Sn13 and Na7Sn12 shows that only the perfectly charge balanced Na7Sn12 is a semiconductor whereas Na5Sn13 is metallic. The rather specific electronic situation in the ternary compound is traced back to the loosely bound Bi atom, which acts as a guest atom according to Bix@Na13Sn27‐x‐yBiy, with x=1 and y=0.27, capable to change its oxidation state and thus to uptake additional electrons to form a semiconductor. Na13Sn25.73Bi1.27 is a rare example of an open framework structure of Sn atoms comprising Bi atoms in the cavities.

Effect of anisotropy field on the resonance frequency and reflection loss shift characteristics of barium hexaferrite ceramics

Abstract For this study, a modified barium hexaferrite based microwave and radar absorbing material was used. Synthesis and characterization of BaFe(12-2x)(MnTi)xO19 (0.1 ≤ x ≤ 1.0) have been prepared by solid state reaction method. The X-ray diffraction patterns reveal that all samples only crystallized into M-type barium hexaferrite after calcination at 1200 °C. Surface morphology images show that the hexagonal flake-like particle is formed at the initial stages of the Mn-Ti substitution level. The magnetic properties measurement reveals that the variation of magnetization values may vary based on preferable site occupation of Mn4+-Ti2+ cations to replace Fe3+ cations. The significant decrease in field coercivity (Hc) from 3.18 kOe to 0.51 kOe with the increase of Mn-Ti substitution affected the lowering values of field anisotropy (Ha). The maximum reflection loss (RL) positions of BaFe(12-2x)(MnTi)xO19 compositional series are shifted to lower frequency range following the Ha trendlines. The maximum RL value equals to 98.42% microwave absorption at 10.5 GHz has been obtained in x = 1.0 (BaFe10Mn0.5Ti0.5O19) composition.

Differential adsorption of H2S/CH4 by bituminous coal and its competitive adsorption properties

To investigate the adsorption characteristics and competitive adsorption patterns of H2S and CH4 in coal seams, we conducted a combined experimental and molecular simulation study using Ningxia Shuangma bituminous coal as the research subject. The experiments examined the adsorption of single-component H2S and CH4 gases at different temperatures and pressures, while the molecular model of bituminous coal was used to analyze the adsorption patterns of binary gas mixtures under competing conditions. Our experimental results demonstrate that both H2S and CH4 follow Langmuir’s model, with their saturated adsorption positively correlated with pressure but negatively correlated with temperature. Moreover, under identical conditions, H2S exhibits 2.43 times higher saturated adsorption than CH4. Molecular simulations reveal that temperature has a greater impact on H2S compared to CH4; both gases undergo reversible physisorption, where isosteric heat of adsorption decreases linearly with increasing amount of adsorbate molecules; interaction energy for H2S is larger in absolute value than that for CH4, indicating its stronger affinity towards coal surfaces; regarding binary component adsorption, an increase in proportion of H2S within the gas mixture leads to higher saturation adsorptions for both the mixture itself and individual H2S molecules while decreasing saturation adsorption for CH4; Coal adsorption selectivity factor for H2S/CH4 > 1. The preferential occupation of high-energy adsorption sites is more likely to be observed for H2S. The adsorption capacity and competitive adsorption capacity of H2S were greater than that of CH4.

Conduction channel creation by interstitial site engineering in otherwise insulating Na6ZnS4 for Na-conducting solid-state electrolytes

Na5.6Zn0.6Ga0.4S4, which retains the crystalline structure of its parent form Na6ZnS4, is described as a new class of Na-conducting solid-state electrolytes (SSEs) for all-solid-state batteries. We demonstrate that while Na6ZnS4 is ionically insulating (1.4 nS cm-1), Ga-substitution results in an astonishing improvement of ionic conductivity (σion) to 70.1 μS cm-1, making Na5.6Zn0.6Ga0.4S4 a practical SSE. This dramatic increase in σion (5 × 104 fold) is associated with an increased Na+ occupancy in interstitial sites as ‘x’ increases in Na6-xZn1-xGaxS4, where interstitial Na ions facilitate long-range Na+ conduction, which is otherwise immobile. Ga-substitution also results in phase-pure Na6-xZn1-xGaxS4, contributing at least partially to the enhancement of σion. Furthermore, Na6-xZn1-xGaxS4 exhibits neither releasing H2S gas nor compromising its crystalline structure for several hours under ambient conditions. Ga-substitution also enhances electrochemical stability. While the anodic limit remains largely unchanged, the cathodic limit is significantly lowered from 0.99 V vs. Na2Sn in Na6ZnS4 to 0.35 V in Na5.6Zn0.6Ga0.4S4, resulting in stable Na alloying/dealloying reactions in a symmetric Na2Sn ‖ Na2Sn cell. These findings are comprehensively supported by various experimental and theoretical methods. Finally, we construct a full cell (Na2Sn ‖ TiS2) and demonstrate the practicality of Na5.6Zn0.6Ga0.4S4 as a promising SSE in all solid-state Na ion batteries.

Spectral Investigation of Enhanced Orange Emission in Eu3+ Activated LaPO4 Nanophosphors Through Codoping With Na+ and Bi3+ Ions.

Lanthanum phosphate is a well-known potential host for rare earth activators for phosphor-converted white LED application. Na+ and Bi3+ codoped Eu3+ activated LaPO4 nanophosphor is successfully synthesized using citrate-based hydrothermal method at ambient condition and confirmed by XRD, EDS and XPS analysis. The excitation spectra of the sample exhibit sharp f-f characteristics peak of Eu3+ at 393 nm that is found to be the most dominant. The comparative photoluminescence studies of La1-xPO4:xEu3+(x = 0.10), La1-x-y PO4:xEu3+, yNa+(x = 0.10, y = 0.05), and La1-x-y-zPO4:xEu3+, yNa+, zBi3+ (x = 0.10, y = z = 0.05) reveal a progressive enhancement of the orange emission from Eu3+ as Na+ and (Na+, Bi3+) ions are incorporated into the LaPO4 matrix. The dominance of 5D0-7F1 magnetic dipole transition contributing a major part of orange luminescence of the nanophosphors and the symmetric site occupancy of Eu3+ was justified from the observed trend of in the Judd-Ofelt intensity parameters. The CIE studies confirm the improvement in color purity of emission from 32.5% to 90.6% due to the presence of Na+ and Bi3+ions.

Origin of the distinct site occupations of H atom in hcp Ti and Zr/Hf

The location of the H atoms in Ti, Zr, and Hf is crucial to the formation of the hydrides in these metals as it influences the crystal lattice transformation and the hydrogen diffusion involved in the hydride formation process. Although Ti, Zr, and Hf are all of hexagonal close-packed structure with similar lattice parameters, the solute H atom occupies the octahedral interstice in Ti but the tetragonal interstice in Zr and Hf, of which the origin is still mysterious. In the present work, the origin of the distinct site occupation behavior of H atom in Ti and Zr/Hf is investigated through first principles calculations. The calculated solution energies confirm that H prefers the octahedral interstice in Ti but the tetrahedral interstice in Zr and Hf. We ascribe the distinct site occupations of H in Ti and Zr/Hf to the varying Coulomb repulsion between the H (as a screened proton in the metals) and the matrix atoms against the interstitial size. The competition between the H-induced electron accumulation effect and the matrix atom debonding effect might matter as well. We propose that, as a general rule, a H atom prefers the site with a trade-off between a large space and a high electron density in metals.

Modulating charge transfer and constructing synergistic bimetallic active sites for CO-SCR reactions in inverse spinel

The selective catalytic reduction of NO by CO (CO-SCR) are frequently catalyzed by spinel due to its exceptional stability and redox capabilities. In this research, a ternary metal-based inverse spinel catalyst Cu0.67Mn0.33Fe2O4 was synthesized utilizing the glycerol self-templating technique. Some Fe3+ (Fe3+Td) sites are transferred to vacant octahedral sites through the occupancy of tetrahedral sites by Mn species. Mn3+ (Mn3+Td) sites synergistically interact with Cu2+ and Fe3+ ions on the octahedral sites to promote charge transfer, producing numerous oxygen-defective and highly mobile oxygen species and constructing Cu+-Ov-Fe2+ active sites on the surface. Various characterizations demonstrated that Cu+-Ov-Fe2+ has greater catalytic activity, resistance to alkali metals, and water toxicity than the Cu2+-Ov-Fe2+ active site of CuFe2O4. In situ DRIFTS further revealed the reaction mechanism of the ternary metal-based inverse spinel catalyst, and this study provides novel perspectives on the development of Cu-based catalysts for CO-SCR.

Improved Dopant Fraction Variance Estimation in Statistical ALCHEMI Based on Correct Error Propagation Rule.

This report revisits the statistical atom location by channeling enhanced microanalysis (St-ALCHEMI) method, correcting the dopant site occupancy error by applying an appropriate error propagation rule. A revised equation for calculating the uncertainty in the determined dopant fractions is proposed. The revised equation is expected to correct the uncertainty in the determined dopant fractions, which is particularly significant in cases of low dopant concentrations and variable dopant occupancies across inequivalent host atomic sites. The approach is validated using Eu-doped Ca2SnO4 as a typical model system.

Achieving Flat Ultra‐Broadband NIR Emission in Cr3+ Doped Garnet‐Type Phosphors Enabled by Structural Regulation Toward Multi‐Functional Spectroscopy Applications

AbstractCr3+‐activated near‐infrared (NIR) emitting phosphors are considered as one of the most potential light‐conversion materials for NIR phosphor converted light‐emitting diodes (NIR pc‐LEDs). However, it is still a challenge for a single Cr3+ ion to achieve a flat ultra‐broadband emission toward multi‐functional spectroscopy applications. Herein, a chemical unit co‐substituting strategy is utilized to regulate the crystallographic occupancy of Cr3+ ions, and a flat ultra‐broadband NIR emission is successfully realized with a record emission wavelength of 915 nm in garnet‐type phosphors Ca3Sc2‐xHfxAlxSi3‐xO12: yCr3+ (0 ≤ x ≤ 1, 0.02 ≤ y ≤ 0.06), together with a large full width at half maximum (FWHM) regulation from 130 to 250 nm. The relation between the site occupation of Cr3+ ions in disordered [CaO8], [(Sc, Hf)O6] and [(Si, Al)O4] polyhedrons and the corresponding NIR emission are clarified by carefully evaluating the structural evolution, Raman spectra, electron paramagnetic resonance and time‐resolved emission lifetime spectra of Cr3+ ions. The corresponding crystal field strength of Cr3+ ions is investigated to further clarify the multi‐sites induced flat broadband NIR emission. Finally, a blue light pumped NIR pc‐LED is fabricated with a total output power of 37.58 mW and photoelectric conversion efficiency (PCE) of 13.67%@100 mA, which realizes the multi‐functional applications in night vision imaging, non‐destructive detection and palmprint vein recognition for assistant medical treatment.

Roads and Woody Vegetation Structure Are Associated With Chimpanzee (Pan troglodytes) Occurrence at Its Northern Range Limit

ABSTRACTAimThe purported defining features of chimpanzee (Pan troglodytes) biogeography are sometimes simplistic and contradictory, yet we rely on these metrics to shape conservation and management planning for this endangered ape. We analysed the cover and configuration of woody vegetation at the northern margins of the species' range in Senegal to elucidate key predictors of chimpanzee biogeography.LocationSoutheastern Senegal.TaxaWestern chimpanzee (Pan troglodytes verus).MethodsWe combined reconnaissance surveys and interviews with published accounts of chimpanzee presence to verify previous estimates of the range limits of the species. High‐resolution, multispectral satellite images were used to quantify the configuration of trees and shrubs at each site. Woody vegetation cover and physiognomy, river density and road density were compared within and outside of the species range with generalised linear mixed models.ResultsOur surveys and interviews support the current estimates of the northern limits of the species range. Chimpanzee‐occupied sites had more patchily‐distributed vegetation, greater patch edge complexity, and slightly higher river density than unoccupied sites. Unoccupied sites had more woody vegetation cover and higher road density. Of all predictors, roads had the highest impact on chimpanzee occupancy.Main ConclusionsIn line with previous findings, anthropogenic modifications of the landscape had a strong impact on chimpanzee occupancy, but surprisingly, woody vegetation cover was negatively associated with chimpanzee occupancy in this region. Instead, more specific metrics of vegetation configuration were positively associated with chimpanzee site occupancy, indicating that precise measures are needed for assessing chimpanzee biogeography at the landscape scale.

Composition Determination of Heterometallic Trinuclear Clusters via Anomalous X-ray and Neutron Diffraction.

Anomalous X-ray diffraction (AXD) and neutron diffraction can be used to crystallographically distinguish between metals of similar electron density. Despite the use of AXD for structural characterization in mixed metal clusters, there are no benchmark studies evaluating the accuracy of AXD toward assessing elemental occupancy in molecules with comparisons with what is determined via neutron diffraction. We collected resonant diffraction data on several homo and heterometallic clusters and refined their anomalous scattering components to determine metal site occupancies. Theoretical resonant scattering terms for Fe0, Co0, and Zn0 were compared against experimental values, revealing theoretical values are ill-suited to serve as references for occupancy determination. The cluster featuring distinct cation and anion metal compositions [CoCp2*][(tbsL)Fe3(μ3-NAr)] was used to assess the accuracy of different f' references for occupancy determination (f'theoretical ± 15-17%; f'experimental ± 10%). This methodology was applied toward calculating the occupancy of three different clusters: (tbsL)Fe2Zn(py) (6), (tbsL)Fe2Zn(μ3-NAr)(py) (7), and [CoCp*2][(tbsL)Fe2Zn(μ3-NAr)] (8). The first two clusters maintain 100% Fe/Zn site isolation, whereas 8 showed metal mixing within the sites. The large crystal size of 8 enabled collection of neutron diffraction data which was compared against the results found with AXD. The ability of AXD to replicate the metal occupancies as determined by neutron diffraction supports the AXD occupancy methodology developed herein. Furthermore, the advantages innate to AXD (e.g., smaller crystal sizes, shorter collection times, and greater availability of synchrotron resources) versus neutron diffraction further support the need for its development as a standard technique.

PlmCas12e Utilizes Glu662 to Prevent Cleavage Site Occupation by Positively Charged Residues Before Target Strand Cleavage

CRISPR-Cas12e is a recently identified gene-editing tool mainly known because its relatively small size benefits cell delivery. Drastically different from Cas9, it creates a blunt-end double-strand breakage of the DNA via two cleavage sites; Cas12e produces a sticky-end double-strand breakage of the DNA through only one cleavage site in its RuvC domain, meaning two consecutive cleavage events first on the non-target strand (ntsDNA) and then the target strand (tsDNA). Though crucial for Cas12e’s cleavage efficiency, the mechanism by which Cas12e loads tsDNA for the second cleavage remains elusive. Through molecular dynamics simulations and our recently matured traveling-salesman-based automated path-searching (TAPS) algorithm, we identified a series of positively charged residues (Arg856TSL, Arg768RuvC, Lys898TSL, Arg904TSL, Arg764RuvC) that guide the tsDNA backbone toward the cleavage site of wild-type PlmCas12e. Further simulations of the R856L and R904L mutants supported such observations. More interestingly, we found the key role of Glu662RuvC in coordinating Arg764RuvC, preventing its occupation of the cleavage site, and facilitating tsDNA cleavage. Additional simulations confirmed that mutating Glu662RuvC to valine disabled such coordination and created a stable intermediate state with Arg764RuvC occupying the cleavage site before tsDNA loading. These insights, revealing an elaborate mechanism of cleavage facilitation, offer essential guiding principles for future rational engineering of Cas12e into more efficient gene-editing tools.

Mechanistic study of β-Ga2O3 nitridation by RF nitrogen plasma for GaN heteroepitaxy

The transformation of 2¯01β-Ga2O3 to h-GaN under exposure to RF nitrogen plasma was monitored in situ by reflection high-energy electron diffraction. Analysis of the reaction kinetics reveals that the nitridation process is initiated by the formation of an oxynitride phase and proceeds via two-dimensional nucleation and growth of wurtzite GaN grains. X-ray photoelectron spectra suggest a Ga−(NxO1−x) type configuration dominates the surface early in the nitridation process. The surface restructuring is followed by a diffusion-fed phase transformation, which propagates the wurzite GaN structure into the substrate upon reaching 70% nitrogen anion site occupation, corresponding to the oxygen solubility in h-GaN. A direct correlation is observed between the nitridated film morphology and the epitaxial film crystallinity, demonstrating control of the residual strain, lateral coherence, and mosaicity in subsequent GaN epitaxy by the nitridation conditions. This study provides mechanistic details of the nitridation reaction of 2¯01β-Ga2O3 facilitating the optimization of the nitridation process toward improving GaN-2¯01β-Ga2O3 heterojunctions.

Barn Owl (Tyto alba)† Habitat Suitability, Nest Box Occupancy, and Management Implications Based on Kentucky Surveys 2010–2022

ABSTRACT Barn Owls (Tyto alba) are a species of conservation interest, but management of nesting populations can require significant effort. To focus management activities, we conducted analyses of statewide survey data collected for Barn Owl nests (n = 515) and roosts (n = 145) in Kentucky, USA, from 2010–2022. Nest and roost sites included natural (e.g., trees, rock shelters) and human-made (e.g., barns, attics, hunting blinds, silos, etc.) structures and nest boxes (n = 270) installed on various substrates. Using data related to land cover, agricultural features, and other habitat-related variables, we examined factors influencing Barn Owl site occupancy by creating habitat suitability models. Additionally, we assessed changes in nest box occupancy over time and the factors that influenced nest box occupancy. The Shannon habitat diversity index and number of buildings within 75 m were the most important variables for habitat suitability throughout the study area, though the proportion of hay/pasture/grassland within 625 m and distance to an area intensively managed for Barn Owls were important regionally. Barn Owl nest box occupancy increased over the course of our study, likely due to management efforts. Owls were more likely to occupy nest boxes if they were installed on tall feed silos, retired utility poles, or barns. Moreover, nest boxes installed at sites where we observed owl pairs (prior to installation) were more likely to become occupied and used sooner than nest boxes installed opportunistically. Future management should focus on installing nest boxes for known pairs, on unused feed silos, on retired utility poles on reclaimed surface mines, and near areas intensively managed for the species.

The Role of the International Community in Stopping the Zionist Aggression on the Gaza Strip

On October 7, 2023, Hamas began its military operation, dubbed the "Al-Aqsa Flood," which consisted of a massive and intensive missile attack that included the launch of 5,000 rockets that Iron Dome failed to confront. It targeted Israeli settlements from Dimona in the south to Hod Hasharon in the north and Jerusalem in the east. In conjunction with the missile attack, it bypassed the Palestinian youth resistance, which is divided into 14 attacking groups by means of vehicles, bicycles and gliders on settlements and military sites of the Zionist occupation in the vicinity of 40 km in the Gaza envelope, thus bypassing the separation wall, which former Israeli Defense Minister Benny Gantz described as "the smart defense marvel." Israel responded to the military operation with a devastating aerial bombardment to start its devastating war against Gaza.

The Cloud People of Naupallacta: Middle Horizon Camelid Management in the Hinterland of the Chicha Soras Valley

Archaeological, ethnographic, and rural development work over the past 50 years in the Chicha Soras area has revealed that the region was first intensively used from the Middle Horizon Epoch 2 (AD 680/700–900) onward. An introduced population here had its seven occupation sites focused on the southern part of the Chicha valley and supported agriculture and textile production, while settlement in the upper Rio Yanamayo and west of the Rio Huayllaripa comprising the Naupallacta complex, served the management of camelid herds, which provided transport, fiber, and meat resources. The interrelationship between the arable farmers and camelid pastoralists produced a mutually supportive resource base for the local agropastoral community, and tribute produced for distant elite Wari administrators. This is confirmed by the interdisciplinary data sets presented here, including demographic, architectural, artefactual, archaeozoological, paleoenvironmental and aDNA results.

Invertebrate-biased diet of burrowing owls in a newly-restored coastal grassland

Recovering biodiversity across trophic levels is a major challenge in restoration ecology. Specifically, predator population recovery depends on the timely re-establishment of their preferred prey species in restored habitats. Here, we evaluate potential dietary factors contributing to the loss of western burrowing owls (Athene cunicularia hypugaea (Bonaparte, 1825)) from a newly-restored coastal grassland. We examined owl pellets and found that burrowing owl diets were relatively low in vertebrate prey during their brief occupation of the restoration site (2.6% of prey items; found in 61.8% of sampled pellets). We suggest that preferred food limitation may have been one contributor to the loss of owls from the restoration site. These findings suggest the need to prioritise re-establishment of prey communities for effective long-term recovery of burrowing owls in restored landscapes.

Developing single ligand strategy for engineering a high-performance photocatalyst with the pore space partition and open-metal sites

Realizing the precise structure design and functional customization of photocatalysts is essential for achieving high conversion and selectivity. Herein, we propose an innovative pore space partition strategy for constructing a high-performance photocatalyst from a single ligand by regulating the group modification and symmetry of the ligand, which solves the problem of open-metal sites occupation. A novel polyoxometalate-based metal-organic framework, CoW–BTIz, was synthesized successfully from a new donor-acceptor-donor type photosensitizer 4, 7-bis (imidazolyl) benzothiazole, Co cations and electron sponge [BW12O40]5– anions. The push−pull effect of the D–A–D units in the confined spatial ensures the charge rapid transport processes. Incorporating POM into photoactive MOF is beneficial to produce single •O2– via type I pathway primarily in air atmosphere by photogenerated electron transfer. CoW–BTIz gave a high yield in the aerobic synthesis of 2-arylbenzothiazole and the cyclization of thioamide to 1,2, 4-thiadiazole by the synergetic effect of each component in mild conditions.