Lattice Positions Research Articles

Inorganic remote glass film based on yellowish‐green (Y, Ba)3(Al, Si)5O12:Ce garnet phosphor for warm white LEDs

AbstractCompared with other fluorescent crystal phases, garnet has better structural stability in a glass matrix and renders precisely controllable emissions due to the abundant lattice control positions. In this work, we regulate the coordination field of Ce3+ ion based on the co‐substitution method and achieve the spectra regulation in the yellow–green range. We used Ba2+–Si4+ cations to replace Y3+–Al3+ cations in Y3Al5O12 (YAG) matrix to obtain blue‐shift of the emission peak from 552 to 539 nm. The centroid shift and crystal field splitting decrease with the decreasing covalency of the bond between the Ce3+ ion and the surrounding anions owing to the higher electronegativity of Si4+ ions than Al3+ ions. The corresponding fluorescent films were prepared by a low‐temperature co‐sintering process based on the as‐made Ba2+–Si4+ co‐substituted phosphor. X‐ray powder diffractometer and scanning electron microscopy images showed that the fluorescence crystals were less eroded and evenly dispersed in the glass matrix. Spectral analysis showed that the garnet phase was protected by using lead‐free borosilicate glass with a low melting point, and the quantum efficiency of phosphor‐in‐glass (PiG) retains 98% of the corresponding phosphor. By adjusting the ratio of garnet phosphor to commercial red nitride phosphors, a warm white fluorescence with a color rendering index of 80.3 and color temperature of 3899 K was obtained. The prepared warm white film has potential application value in the whole spectra field.

Electrolyte Permeability in Plastic Ice VII.

Deep brines in water-rich planets form when electrolytes diffuse from the rocky interior through layers of thick dense ice such as ice VII and the hypothesized plastic ice VII. We perform classical molecular dynamics simulations of Li+, Na+, and K+ alkali ions and F- and Cl- halide ions in plastic ice VII at conditions similar to water-rich super-Earths, icy moons, and ocean worlds. We find that plastic ice VII is permeable to electrolytes on geological timescales. Diffusion occurs via jumps between adjacent voids in the bcc crystal structure and is governed by molecular rotations. An exception to this mechanism is Na+ which, at variance with other ions, can substitute water molecules on lattice positions. The bulk modulus of pristine plastic ice VII is dependent on the pace of molecular rotations: when the rotations are slow, the bulk modulus is 1 order of magnitude lower compared to the bulk modulus at conditions of fast rotations, hence providing direct evidence of the role of molecular rotations in determining elastic properties. Electrolytes affect the bulk modulus only at high-concentration conditions and slow molecular rotations. Our results show that plastic ice VII may facilitate the development of brines in water-rich planets and ocean worlds, with a clear significance for their potential to support exobiology and for the chemical evolution of their aqueous reservoirs.

Surface engineered phosphorene using boron and arsenic doping/Co-doping for Co-optimizing the adsorption stability, transduction, and recovery of CO, NO, and SO gases – A density functional theory perspective

In this work, for the first time, the effects of non-metallic Boron (B), Arsenic (As) substitutional doping as well as co-doping at different lattice positions of monolayer Phosphorene (Ph) have been extensively investigated for Carbon Monoxide (CO), Sulphur Monoxide (SO), and Nitrogen Monoxide (NO) adsorption using first principle calculation. The electronic configurations and effects of relative dopant positions (for co-doping) on atomic sub-planes of Ph significantly influence the molecular adsorptions of these monoxides, whereas the charge transfer is dominated by the molecular orientations and charge distributions of the gas molecule and host atoms near adsorption sites. The B doping notably increases the adsorption strength for each monoxide, wherein As doping increases the adsorption for CO and NO adsorption and reduces the strength for SO compared to pristine Ph. In contrast, B/As co-doping significantly and moderately increases the strength of CO/NO and SO adsorption, respectively. The co-doping exhibits a shorter recovery time while retaining adsorption stability for CO and NO. Moreover, doping/co-doping notably increases the charge transfer after NO adsorption. Finally, the NO and SO adsorptions severely alter the distribution of electronic states near the band edges, which results in significant modulations in the energy band structure of the co-doped lattice.

Lattice position optimization for LATTICE therapy.

LATTICE radiation therapy delivers 3D heterogenous dose of high peak-to-valley dose ratio (PVDR) to the tumor target, with peak dose at lattice vertices inside the target and valley dose for the rest of the target. Although the lattice vertex positions can impact PVDR inside the target and sparing of organs-at-risk (OAR), they are fixed as constants and not optimized during treatment planning in current clinical practice. This work proposes a new LATTICE plan optimization method that can optimize lattice vertex positions during LATTICE treatment planning, which is the first lattice position optimization study to the best of our knowledge. The new LATTICE treatment planning method optimizes lattice vertex positions as well as other plan variables (e.g., photon fluences or proton spot weights), with optimization objectives for target PVDR and OAR sparing. To satisfy mathematical differentiability, the lattice vertices are approximated in sigmoid functions. For geometric feasibility, proper geometry constraints are enforced onto lattice vertex positions. The lattice position optimization problem is solved by iterative convex relaxation (ICR) method and alternating direction method of multipliers (ADMM), and lattice vertex positions and photon/proton plan variables are jointly updated via the Quasi-Newton method. Both photon and proton LATTICE RT were considered, and the optimal lattice vertex positions in terms of plan objectives were found by solving all possible combinations on given discrete positions via exhaustive searching based on standard IMRT/IMPT, which served as the ground truth for validating the new LATTICE method. The results show that the new method indeed provided the optimal lattice vertex positions with the smallest optimization objective, the largest target PVDR, and the best OAR sparing. A new LATTICE treatment planning method is proposed and validated that can optimize lattice vertex positions as well as other photon or proton plan variables for improving target PVDR and OAR sparing.

Plasma-Assisted N-Doped TiO2 Nanotube Array as an Active UV–vis Photoanode

This work shows the possibility of using plasma nitriding under ultra-high-vacuum conditions to introduce nitrogen into a titanium dioxide structure in the form of nanotubes with a diameter of about 110 nm. Nanotubes were produced by the anodic oxidation of Ti foil in a solution based on glycerine and water with the addition of ammonium fluoride at a voltage of 25 V. Based on experimental evidence obtained by X-ray photoelectron spectroscopy (XPS, in situ), it has been shown that alternating nitriding and annealing processes at 450 °C leads to formation of Ti-N-O, Ti-N, and Ti-O-N chemical bonds in the TiO2 crystal structure (anatase). The observed changes were identified as interstitial or substitutional admixtures or variations of these. The spectrophotometric and spectrophotoelectrochemical tests performed showed that the photoactivity of the photoanodes doped with nitrogen and annealed at 450 °C in the UV–vis range was significantly greater than that of the photoanodes without nitrogen. The highest maximum photocurrent density, of about 30.0 μA·cm–2 at a wavelength of λ = 350 nm, was obtained for the double-nitrided and once-annealed sample, where nitrogen was mainly incorporated in the interstitial positions in the TiO2 lattice. For the materials not nitrided as well as annealed only at 450 °C and pristine, the worse photoresponse was received at the levels of ∼16 and ∼0.2 μA·cm–2, respectively. The thermo-chemical treatment applied also effectively extended the operational range of the photoanodes toward visible light, where a wide maximum of light absorption was observed from ∼400 to ∼700 nm, with a maximum wavelength of 550 nm and an estimated bandgap energy of 2.5 eV. Our investigations confirmed that photoelectrochemical (PEC) performance for TiO2 NT-based photoanodes was achieved by the optimum annealing condition and concentration of nitrogen, where the narrowed bandgap was observed by generating a new N 2p energy level above the O 2p valence band. The following research techniques were used to identify the changes taking place in the materials produced: XPS spectroscopy, UV–vis spectroscopy, PEC measurements, X-ray diffraction structural measurements, and scanning electron microscopic observations.

Grain boundary segregation of nickel vacancies and space charge zone formation in NiO through interactions among Ni2+, O2−, and Ni3+

Defects like nickel vacancies (VNi″), holes (Ni3+) with different segregation tendencies to grain boundary (GB) can govern the properties of nickel oxide (NiO) – a promising material for energy applications. An atomistic model of non-stoichiometric NiO bicrystal with θ°001100 GB is developed to understand the segregation of VNi″, Ni3+ to GB from various ionic interactions. According to the model lattice positions available for VNi″ in GB possess lower attractive (from Ni2+-O2− interactions) and higher repulsive (from Ni2+-Ni2+ interactions) energies when compared with those in grain interior. This is due to the differences in these inter-ionic distances in GB and grain interior. Hence VNi″ segregate to GB. Contrarily, grain interior is more favorable for formation of Ni3+ in GB. These Ni3+ form a space charge zone adjacent to the GB. The model helps in understanding VNi″ segregation to GB and space charge zone formation.

Mobile oxygen in layered nickelates of perovskite-type

The influence of the different types of oxygen on the structure and electrical conductivity of the perovskite-type nickelates were investigated. The nickelates La2NiO4+δ, La0,6Sr1,4NiO4–δ, Sr3Al0,75Ni1,25O7–δ were synthesised using the solidstate reaction route. Phase composition was determined by X-ray powder diffraction analysis. The iodometric titration technique was used to specify the oxygen content of the powders. Oxygen desorption and absorption, including oxygen index variation, were investigated by oxygen solid electrolyte coulometry (OSEC). Electroconductive properties of samples were studied by a standard DC four-point method. Utilizing OSEC technique, three mobile and one regular type of oxygen were observed in the perovskite layered nickelates with P/RS and 2P/RS structure. These four types of mobile oxygen differ in the binding energy to the crystal lattice and crystallographic positions. The desorption-sorption processes of various types of mobile oxygen have different effects on the thermal expansion of crystal lattice parameters. The regular oxygen, occupying the apex of octahedron, affects the lattice parameters most prominently. This type of oxygen changes the character of the temperature dependence of specific resistivity sufficiently. Interstitial oxygen does not yield such anomalies.

Isomorphous and Isostructural Coordination Polymers Besides Metal‐Organic Frameworks (MOFs) of bis(4‐Nitrophenyl)‐phosphoric Acid in Conjunction with Some N‐donor Compounds

AbstractVarious coordination complexes, in the form of infinite coordination polymers and metal‐organic frameworks (MOFs) of an organophosphorous acid, bis(4‐nitrophenyl)phosphoric acid (BNPP), in the presence of some N‐donor compounds like 4,4′‐bipyridine (bpy), 1,2‐bis(4‐pyridyl)ethene (bpyee), 1,2‐bis(4‐pyridyl)ethane (bpyea) and 1,3‐bis(4‐pyridyl)propane (bpypa) along with metal ions, Co+2, Cd+2, Cu+2, and Ni+2, have been reported. Using the single crystal X‐ray diffraction method, the obtained structures are classified into isomorphous, isostructural coordination polymers, and metal‐organic framework structures. Except for the structures, formed by bpy with Ni(II) and Cu(II), bpypa with Cu(II) and bpyee with Co(II) and Ni(II), all of the complexes crystallize with both BNPP and N‐donor ligands forming coordinate bonds with the metal ions, yielding dumbbell‐shaped moieties in the lattices. A noteworthy feature in the structures obtained with bpyee, is that BNPP molecules do not form coordination bonds with metal ions Co(II) and Ni(II), while N‐donor ligands (bpyee) are only connected to the metal ions. Furthermore, in these complexes, the BNPP molecules occupy the same positions in the crystal lattice as those of coordinated BNPP moieties, but by hydrogen bonds, thus, establishing a high correlation of isostructurality in three‐dimensional packing between structures having coordinated and uncoordinated BNPP molecules, and highlighting the significance of hydrogen bonds in comparison with coordinated bonds. All of the complexes described, herein, are stabilized by different types of intermolecular interactions, specifically through a large number of C−H⋅⋅⋅O hydrogen bonds. Hirshfeld analysis further demonstrates surface properties and establishes accountability of various intermolecular interactions towards the stabilization of the complexes, emphasising, in particular, the importance of the C−H⋅⋅⋅O hydrogen bonds

Impact of d-states on transition metal impurity diffusion in TiN

In this work, we studied the energetics of diffusion-related quantities of transition-metal impurities in TiN, a prototype ceramic protective coating. We use ab-initio calculations to construct a database of impurity formation energies, vacancy-impurity binding energies, migration, and activation energies of 3d and selected 4d and 5d elements for the vacancy-mediated diffusion process. The obtained trends suggest that the trends in migration and activation energies are not fully anti-correlated with the size of the migration atom. We argue that this is caused by a strong impact of chemistry in terms of binding. We quantified this effect for selected cases using the density of electronic states, Crystal Orbital Hamiltonian Population analysis, and charge density analysis. Our results show that the bonding of impurities in the initial state of a diffusion jump (equilibrium lattice position), as well as the charge directionality at the transition state (energy maximum along the diffusion jump pathway), significantly impact the activation energies.

Site preference-based luminescence studies in Eu doped calcium magnesium silicate phosphor: A combined experimental and DFT approach

The luminescence of Eu3+ doped calcium magnesium silicate (CMS: Eu3+) phosphor is studied experimentally by optimizing the single diopside structure in the solid state reaction method and theoretically verified using the first principle density functional theory (DFT) calculation. Field Emission Scanning Electron Microscopy (FESEM) analysis shows a transition from agglomerated morphology to particle formation at 900 °C. A combination of diopside and akermanite structures are formed at 800 °C, whereas a single diopside phase is optimized from 900 °C onwards. DFT calculation has been carried out to identify the lattice parameters of the diopside structure of calcium magnesium silicate (CMS) and Eu3+ doped CMS by replacing Eu3+ in the lattice site of Ca and Mg to identify the stable structure. The lattice expansion is minimal when Eu3+ replaces the Ca2+ position. Lattice parameters of the diopside phase calculated using Rietveld refinement of the XRD pattern are in agreement with DFT findings. FTIR analysis confirms a redshift corresponding to Ca–O and a blueshift corresponding to Mg–O stretching wavenumbers due to the structural modification of CMS due to Eu addition in the lattice. The stability and site preference of Eu3+ ion in CMS is determined from the mixing energy (ΔHm) of Eu doped in the Ca site and Mg site of CMS separately via DFT calculation and confirm that the mixing energy is minimum when Eu3+ replaces Ca lattice position. UV–visible, DRS spectroscopy confirms a bandgap of ∼6 eV for CMS and CMS: Eu3+. Luminescence studies confirm constant peak splitting in the 5D0→7FJ (J = 1,2,4) transitions due to the crystal field effect caused due to the incorporation of Eu3+ in the diopside structure with dodecahedral coordination. Eight coordinated site preference of Eu3+ in diopside is confirmed via DFT calculations. Modification in asymmetry ratio (R-ratio) with temperature also corroborates with modification in the intensity of photoluminescence spectra dictated by the reduction in inversion symmetry. CIE color chromaticity analysis shows a coordinate of (0.61, 0.39) in the red region of visible spectra with a color purity of 83.49% irrespective of annealing temperature.

Bi3+-activated dual-wavelength emitting phosphors toward effective optical thermometry

Optical thermometry as an important local temperature-sensing technique, has received increasing attention in scientific and industrial areas. However, it is still a big challenge to develop luminescent materials with self-activated dual-wavelength emissions toward high-sensitivity optical thermometers. Herein, a novel ratiometric thermometric strategy of Bi3+-activated dual-wavelength emission band was realized in the same lattice position with two local electronic states of La3Sb1-xTaxO7:Bi3+(0 ≤ x ≤ 1.0) materials based on the different temperature-dependent emission behaviors, benefiting from the highly-sensitive and regulable emission to the coordination environment of Bi3+. The structural and spectral results demonstrate that the emission tremendously shifted from green to blue with 68 nm and the intensity was enhanced 2.6 times. Especially, the visual dual-wavelength emitting from two emission centers was presented by increasing the Ta5+substitution concentration to 20% or 25%, mainly originating from the two local electronic states around the Bi3+ emission center. Significantly, the dual-wavelength with different thermal-quenching performance provided high-temperature sensitivity and good discrimination signals for optical thermometry in the range between 303 and 493 K. The maximum relative sensitivity reached 2.64%/K (La3Sb0.8Ta0.2O7:0.04Bi3+@383 K) and 1.91%/K (La3Sb0.75Ta0.25O7:0.04Bi3+@388 K). This work reveals a rational design strategy of different local electronic states around the single-doping multiple emission centers towards practical applications, such as luminescence thermometry and white LED lighting.

Precise Regulation of Emission Maxima and Construction of Highly Efficient Electroluminescent Materials with High Color Purity

AbstractAdvanced multiple resonance induced thermally activated delayed fluorescence (MR‐TADF) emitters have emerged as a privileged motif for applications in organic light‐emitting diodes (OLEDs), because they furnish highly tunable TADF characteristics and high color purity emission. Herein, based on the unique nitrogen‐atom embedding molecular engineering (NEME) strategy, a series of compounds BN‐TP‐Nx (x=1, 2, 3, 4) have been customized. The nitrogen‐atom anchored at different position of triphenylene hexagonal lattice entails varying degrees of perturbation to the electronic structure. The newly‐constructed emitters have demonstrated the precise regulation of emission maxima of MR‐TADF emitters to meet the actual industrial demand, and further enormously enriched the MR‐TADF molecular reservoir. The BN‐TP‐N3‐based OLED exhibits ultrapure green emission, with peak of 524 nm, full‐width at half‐maximum (FWHM) of 33 nm, Commission Internationale de L'Eclairage (CIE) coordinates of (0.23, 0.71), and maximum external quantum efficiency (EQE) of 37.3 %.

Precisely Slight Regulation of Emission Maxima and Construction of Highly Efficient Electroluminescent Materials with High Color Purity.

Advanced multiple resonance induced thermally activated delayed fluorescence (MR-TADF) emitters have emerged as a privileged motif for applications in organic light-emitting diodes (OLEDs), because they furnish highly tunable bandgap with emission ranges spanning the visible light region, and have the intrinsic properties of outstanding TADF characteristics and high color purity emission. One of the typical construction paradigms of MR-TADF molecule is based on polycyclization of MR parent core and a representative target model molecule BN-TP has been prepared. Herein, based on the unique nitrogen-atom embedding molecular engineering (NEME) strategy, a series of congeners of BN-TP, namely BN-TP-Nx (x = 1, 2, 3, 4), have been customized. The nitrogen-atom anchored at different position of triphenylene hexagonal lattice entails varying degrees of perturbation to the electronic structure. The newly-constructed emitters have demonstrated the precisely slight regulation of emission maxima of MR-TADF emitters to meet the actual industrial demand, and further enormously enriched the MR-TADF molecular reservoir. The BN-TP-N3-based OLED exhibits ultrapure green emission, with peak of 524 nm, full-width at half-maximum (FWHM) of 33 nm, Commission Internationale de L'Eclairage (CIE) coordinates of (0.23, 0.71), and maximum external quantum efficiency (EQE) of 37.3%.

Electronic structure and optical properties of Br- and Cl-doped rutile TiO2 for application in self-cleaning and photovoltaic panel's coatings: first-principle calculations.

Development of novel self-cleaning technologies, especially those based on semiconductor photocatalysis system, is one of the most important research problems in environmental cleanup. Titanium dioxide (TiO2) is a well-known semiconductor photocatalyst that has a strong photocatalytic activity in the ultra-violet part of the spectrum while its photocatalytic efficiency is very limited within the visible range due to its large band gap. In the field of photocatalytic materials, doping is an efficient method to increase the spectral response and promote charge separation. However, the type of dopant is not the only important factor, but also its position in the material lattice. In the present study, we have carried out first-principle calculations based on density functional theory to explore how particular doping configuration, such as Br or Cl doping at an O site, may influence the electronic structure and the charge density distribution within rutile TiO2. Furthermore, optical properties such as the absorption coefficient, the transmittance, and reflectance spectra have also been derived from the calculated complex dielectric function and examined to see whether this doping configuration has any effect on the use of the material as a self-cleaning coating on photovoltaic panels.

The Luminescence Properties of the Interstitial Eu2+ in SrB2O4 for UV Light‐Emitting Diode

SrB2O4:Eu2+ is prepared by the high‐temperature solid‐phase method. The structure is characterized by X‐ray diffraction, and the luminescence properties are analyzed using fluorescence spectroscopy and decay curves. SrB2O4:Eu2+ has strong absorption in the UV region and two broadband emissions in the 350–550 nm, located at 374 and 458 nm. The broadband emission around 374 nm belongs to Eu2+ emission at the Sr lattice position, and the emission around 458 nm belongs to interstitial Eu2+ ions. At low concentrations, Eu2+ replaces the position of Sr2+ first, and the emission peak of 374 nm is stronger than that of 458 nm in the emission spectrum. The luminescence at 458 nm enhances significantly as the concentration of Eu2+ ions increases. The fluorescence lifetime confirms the presence of two luminescent centers, the EuSr and the interstitial Eu2+ ions. The temperature dependence luminescence of SrB2O4:Eu2+ is explored, and the activation energy is calculated to be ΔEa = 0.3622 eV. The Commission Internationale de l'Éclairage (CIE) chromaticity coordinates of SrB2O4:Eu2+ are in the blue area. The results indicate that the interstitial Eu2+ benefits the color‐rendering index when SrB2O4:Eu2+ is used as a blue phosphor in UV light‐emitting diode (LED).

BaCa13Mg2(SiO4)8: Ce3+ — A blue phosphor with high brightness, high internal quantum efficiency and excellent thermal stability for w-LEDs

In this paper, a series of Ce3+ ions doped BaCa13Mg2(SiO4)8 blue phosphors were synthesized via a conventional high-temperature solid-state method. Calculations by DFT confirmed that the BaCa13Mg2(SiO4)8 host had a suitable band gap for doping rare earth ions. In terms of luminescence performance, BaCa13Mg2(SiO4)8: Ce3+ blue phosphor with an optimal excitation wavelength of 365 nm can effectively absorb light from 310 to 400 nm and produce a wide emission band centered at 440 nm with an internal quantum efficiency of 71.39%. Based on the analysis of the structure and Gaussian fitting spectra, the Ce3+ ion can occupy all of the Ba2+ and Ca2+ ion lattice positions. After charge compensation by K+ ions, the emission intensity can be increased by 36.8%, and the emission intensity at 140 °C can still maintain 88.7% compared with that at room temperature. Under 365 nm excitation, the integral intensity of the emission spectrum BaCa13Mg2(SiO4)8: 3% Ce3+, 3% K+ sample can reach 90.4% of that of the commercial blue phosphor BaMgAl10O17: Eu2+. When BaCa13Mg2(SiO4)8: Ce3+ phosphors are combined with green (Ba, Sr)2SiO4: Eu2+ phosphors and red CaAlSiN3: Eu2+ phosphors on a 365 nm UV-LED chip, bright LED devices with a correlated color temperature of 4172 K can be obtained. The results show that the blue phosphor BaCa13Mg2(SiO4)8: Ce3+ has great potential for w-LEDs applications.

Rattling-induced suppression of thermal transport in cubic In2O3 with Sn-Ga diatomic defect

We present the first principles study of cubic In2O3 with a diatomic defect composed of a Sn atom substituting the In atom at the b-site and a Ga atom embedded in the nearest c-site (structural vacancy) with lattice positions according to the Wyckoff notations. Structural, electronic, phononic and thermal properties were investigated within density functional theory formalism. The lattice anharmonicity effects were taken into account for all possible three-phonon scattering processes. The phonon transport was considered within the Peierls-Boltzmann transport equation with relaxation time approximation. In the relaxed lattice, a strong rearrangement of the initial positions of the atoms in the defect vicinity was revealed, which primarily manifests itself in the displacement of the Sn atom toward another interstitial site. Thus, a cage is formed around the defect by 12 O and 12 In atoms. The calculations of elastic constants and mean square displacements of cage region atoms showed the rattling-like behavior of the Sn atom. Bader charge analysis and electron localization function allowed a deeper understanding and explanation of such behavior. Phonon energy spectra as compared to In2O3 and In2O3:(Sn) demonstrated flattening of phonon branches with spatial localization of phonon modes. They also revealed a decrease in average group velocities of phonons, including those of acoustic type, the presence of avoided-crossing features in the low energy range, and an increase of available phase space for three-phonon scattering. Accounting for all these vibrational features due to defect atoms resulted in a thermal conductivity drop at room temperature by more than seven times compared to In2O3.

Observation of a Plastic Crystal in Water-Ammonia Mixtures under High Pressure and Temperature.

Solid mixtures of ammonia and water, the so-called ammonia hydrates, are thought to be major components of solar and extra-solar icy planets. We present here a thorough characterization of the recently reported high pressure (P)-temperature (T) phase VII of ammonia monohydrate (AMH) using Raman spectroscopy, X-ray diffraction, and quasi-elastic neutron scattering (QENS) experiments in the ranges 4-10 GPa, 450-600 K. Our results show that AMH-VII exhibits common structural features with the disordered ionico-molecular alloy (DIMA) phase, stable above 7.5 GPa at 300 K: both present a substitutional disorder of water and ammonia over the sites of a body-centered cubic lattice and are partially ionic. The two phases however markedly differ in their hydrogen dynamics, and QENS measurements show that AMH-VII is characterized by free molecular rotations around the lattice positions which are quenched in the DIMA phase. AMH-VII is thus a peculiar crystalline solid in that it combines three types of disorder: substitutional, compositional, and rotational.

Design of Flame‐Made ZnZrOx Catalysts for Sustainable Methanol Synthesis from CO2

AbstractMixed zinc‐zirconium oxides, ZnZrOx, are highly selective and stable catalysts for CO2 hydrogenation to methanol, a pivotal energy vector. However, their activity remains moderate, and descriptors to design improved systems are lacking. This work applies flame spray pyrolysis (FSP), a one‐step and scalable method, to synthesize a series of ZnZrOx catalysts, and systematically compares them to coprecipitated (CP) analogs to establish deeper synthesis–structure–performance relationships. FSP systems (up to 5 mol%) generally display a threefold higher methanol productivity compared to their CP counterparts. In‐depth characterization and theoretical simulations show that, unlike CP, FSP maximizes the surface area and formation of atomically dispersed Zn2+ sites incorporated in lattice positions within the ZrO2 surface, which is key to improving performance. Analysis by in situ electron paramagnetic resonance (EPR) spectroscopy reveals that the specific architecture of the flame‐made catalyst markedly fosters the generation of oxygen vacancies. Together with surrounding Zn and Zr‐O atoms, the oxygen vacancies create active ensembles that favor methanol formation through the formate path while suppressing undesired CO production, as confirmed by kinetic modeling. This study elucidates the nature of active sites and their working mechanism, pushing forward ZnZrOx‐catalyzed methanol synthesis by providing a new benchmark for this cost‐effective and earth‐abundant catalyst family.

Interpreting equatorial X-ray diffraction patterns from striated muscle with multiscale modeling.

Small-angle X-ray diffraction is the tool of choice to obtain nm-scale structural information from striated muscle under near-physiological conditions. A critical barrier to progress has been the lack of generally applicable computational tools for modeling these X-ray diffraction patterns, limiting our ability to extract all the structural information potentially available. We addressed this need by extending the spatially explicit simulation platform MUSICO to predict equatorial fiber X-ray diffraction patterns from skeletal muscle. Electron densities for thin filaments with bound crossbridges were calculated using PDB structures of myosin S1, actin, tropomyosin, troponin and analogous nebulin structure derived from tropomyosin PDB. Thick filament backbone densities were constructed based on the Squire 1973 model incorporating “ribbon motifs” from a high-resolution cryo-EM structure of the Lethocerus thick filament. Titin and myosin S2 regions were constructed as cylindrical rings of density shells. Myosin heads in an ordered “parked state” were positioned in a shell close to the thick filament backbone with any disordered myosin heads distributed in a shell extending out to actin. X-ray diffraction patterns were calculated from sub-system motifs consisting of 1 thick filament and two thin filaments by evaluating the Fourier transform of this object at the reciprocal hexagonal lattice positions. Intensities were averaged over the 500 thick filaments and 1000 thin filaments used in simulation. Using this approach, we found that we could recapitulate 7 independent experimental intensities (out to the 4,0 reflection) from relaxed rat soleus and EDL muscle by varying only the proportion of heads in the parked state and a temperature factor type disorder term. Fits to contracting data could be achieved by adjusting only the temperature factor term and the number of force-producing crossbridges predicted by MUSICO to match the force levels observed experimentally.