Unusual Geometry Research Articles

Novel carbonate/pyridine tetranuclear nickel complex, exhibiting slow relaxation of the magnetization

Tetranuclear [Ni4(CO3)4(pyridine)8·Na]Cl·pyridine·H2O compound with unusual square-planar geometry was obtained via spontaneous fixation of atmospheric CO2 and its conversion into carbonate bridging ligands. This compound exhibits a slow relaxation of the magnetization caused by a spin-glass behaviour.

A Top‐Down Approach towards Cu(I) Alkynyl Clusters with Unusual Geometry

Main observation and conclusionTo search for novel Cu(I) complexes, traditional approaches focus on designing and screening ligands, metal precursors and reaction parameters. In this report, we propose a top‐down approach, in which Cu precursor is first reduced to nanoparticles in the presence of alkynyl and phosphine ligands. The nanoparticles then undergo an auto‐oxidation step in open air to give CuO powder. During this process, a new tetranuclear Cu(I) cluster with an unprecedented centered triangular configuration, [Cu4(PhC≡C)3(dppp)3]NO3, is isolated in the supernatant. To demonstrate the feasibility of such strategy, it is applied to synthesize another two new Cu(I) clusters, [Cu6 (PhC≡C)5(dppe)3]NO3 and Cu4(PhC≡C)4(dpph)2. The latter has shown a photoluminescence at 511 nm with a quantum yield of as high as 69.84%.

Stack‐and‐Draw Applied to the Engineering of Multi‐Material Fibers with Non‐Cylindrical Profiles

AbstractHere, it is demonstrated that the stack‐and‐draw approach can be expanded to unusual materials association and profile geometries to generate fiber assemblies with unprecedented functionalities. This approach relies on the stacking of flat oxide glass slides into a preform, which is then thermally elongated into tens‐of‐meters‐long ribbon fibers with preserved cross‐section ratio. Fabrication methodology is introduced. In order to illustrate the versatility of the method, a panel of fibers with diverse geometries and functions is exposed, including glass‐only exposed‐core fibers for chemical sensing and, upon the insertion of metal electrodes, H‐shaped multi‐cavity structures and compact, glass‐metal fiber optical detectors applied to a gas analysis by means of fiber‐tip plasma spectroscopy. It is believed this new approach will offer an attractive, straightforward solution for designing innovative, complex multimaterial fiber platforms with enhanced functionalities.

Toward predictive permeabilities: Experimental measurements and multiscale simulation of methanol transport in Nafion

AbstractA polymer membrane's permeability to solutes determines its suitability for various applications: a permeability value is essential for predicting performance in diverse contexts. Using aqueous methanol permeation through Nafion as an example, we describe a methodology for determining membrane permeability that accounts for boundary layer effects and the possibility of swelling. For the materials and apparatus used herein, analysis of a permeance measurement and computational fluid dynamics simulations show that the mass transfer boundary layer is on the order of ones to tens of microns. The data are used to develop and validate a multiscale model describing solute permeation through a hydrated membrane as a series of physical mechanistic steps: reversible adsorption from solution at the membrane interface, diffusion driven by a concentration gradient within the membrane, and reversible desorption into solution at the opposite membrane interface. The validated model is used to predict methanol transport across a solar‐driven CO2 reduction device and to assess the impact of polymer changes on the measured value. The approach of combining experimental data, computational fluid dynamics, and the mechanistic multiscale model is expected to provide more accurate analysis of membrane permeation data in cases with polymer swelling or unusual device geometries, among others.

Hekla Revisited: Fractionation of a Magma Body at Historical Timescales

AbstractHekla is an elongate volcano that lies at the intersection of the South Iceland Seismic Zone and the Eastern Volcanic Zone. We report major and trace element, oxygen isotopic, and H2O analyses on rocks, glass, melt inclusions, and minerals from almost all of the historical lavas and tephra deposits. This new dataset confirms the remarkable observation that not only are many eruptions compositionally zoned from felsic to mafic, but the extent of zoning relates directly to the length of repose since the previous eruption. Compositional data are consistent with the origin of the basaltic andesites and andesites by fractional crystallization, with no measurable crustal interaction once basaltic andesite has been produced. Although the 1104 CE Plinian rhyolite and 1158 CE dacite are also created by fractional crystallization, uranium–thorium isotopic disequilibria measured by others require that they evolved in a separate body, where magma is stored in a molten state for >104 years. Consistent trace element trends and ratios, as well as oxygenisotopic data, preclude significant crustal input into the evolving magma. The phenocryst assemblages are dominated by crystals that formed from their host melt; an exception is the 1158 CE dacite, which contains abundant crystals that formed from the 1104 CE rhyolite melt. A suite of thermobarometers indicates that most crystals formed in the lower crust at temperatures ranging from ∼1010 to 850 °C. Hekla’s unique and systematic petrological time series and geophysical activity are attributed to the unusual geometry of the magma body, which we propose to be a tabular, vertically elongate macrodike, extending from the lower to the upper crust. The vertical body is recharged with basaltic andesite magma at the end of each eruption, which then undergoes cooling and crystallization until the subsequent eruption. The entire system is supplied by a lower-crustal body of basaltic andesite, which is produced by fractional crystallization of basaltic magma in a reservoir that is thermochemically buffered to ∼1010 °C. Cooling and crystallization of recharged basaltic andesite magma in a background geothermal gradient from the lower to the shallow crust accounts for the systematic relationship between repose and composition.

Distortions, deviations and alternative facts: reliability in crystallography.

This feature article is derived from the author's presentation of the Lonsdale lecture at the BCA Spring Meeting in 2018. One of the research results for which Kathleen Lonsdale is best known was her 1929 demonstration that the benzene ring in crystalline hexa-methyl-benzene is planar and has essentially hexagonal symmetry, resolving decades of dispute among organic chemists. More recent crystallographic studies of hexa-methyl-benzene have shown that there are actually small deviations from planarity. Such deviations for aromatic compounds may be due to electronic, steric, and/or intermolecular factors. Some substituted benzene molecules display remarkably large deviations, both from a planar ring structure and from regular hexagonal angular geometry around the ring. Starting from this specific connection with Kathleen Lonsdale's research, a number of stories are recounted of structural distortions and deviations from expected results and explanations that have been suggested for them, across a wide range of chemical topics including macrocycles, metal clusters, unusual coordination geometry and isomerism. On the way we find genuine surprises and results that have led to new understanding, but also examples of poor experiments, misinterpretation of data, scientific bias and preconceived ideas, incompetence and even deliberate fraud. Some aspects of structure validation are discussed. While showcasing some interesting research in its own right, this account also serves an educational purpose.

Computational design technologies for interior designers: a case study

Traditionally interior design is based on the inspiration generated by the designer who acts as an artist and engineer at the same time. Today, a number of digitally developed forms can be used with an aim to offer unusual geometries. Computational design technologies can be used in order to fully automate the generation of a design based on a series of parameters that can be altered within specific limits. In such a way, families of forms and proposals are made available and more opportunities for products dealing with interior design can be produced. These forms require the use of modern 3D printing technologies for their construction due to their geometrical complexity and their digital development. In the present paper, computational design will be presented together with a case study in the area of interior design.

CAD based design for the jewellery industry: A case study

Jewel design is performed for many years and the designers and manufacturers follow a variety of inspirations. Traditionally the designs are generated based on the artistic sense of the creator, while at the same time a number of manufacturing restrictions apply. Nowadays, a series of advanced Computer Aided Design, CAD based tools are available in order to generate impressive concepts. Although, it is possible for designers to interface a CAD system and implement their design digitally, some prefer to use the programming capabilities offered by the CAD software developers. This is the way forward, in order to create unusual geometries for the jewellery industry and at the same time to develop the capability for generating a complete family of geometries that can satisfy even the most demanding customer. In the current paper, the latest approach is presented together with a case study.

High‐Resolution P‐T‐Time Paths Across Himalayan Faults Exposed Along the Bhagirathi Transect NW India: Implications for the Construction of the Himalayan Orogen and Ongoing Deformation

AbstractPressure‐temperature (P‐T) conditions and high‐resolution paths from 11 garnet‐bearing rocks collected across Himalayan fault systems exposed along the Bhagirathi River (Uttarakhand, NW India) reveal the tectonic conditions responsible for their growth. A garnet from the Tethyan metasedimentary unit has a 50.3 ± 0.6 Ma (Th‐Pb, ±1σ) monazite inclusion, suggesting that ductile mid‐crustal metamorphism occurred synchronously or soon after (<10 Myr) India‐Asia collision, depending on timing. High‐resolution garnet P‐T paths from the same rock show ∼1 kbar fluctuations in P as T increases over a ∼20°C interval, consistent with a period of erosion. We report garnets from the Main Central Thrust (MCT) hanging wall that have Eocene to Miocene monazite ages, and one garnet yields paths consistent with motion along the Main Himalayan Thrust (MHT) décollement. Most high‐resolution MCT footwall P‐T paths fluctuate in P (±1 kbar) as T increases, consistent with imbrication and paths from equivalent structural assemblages in central Nepal. Like those rocks, MCT footwall (Lesser Himalayan Formation, LHF) monazite ages are Early Miocene (9.3 ± 0.6 Ma) to Pliocene (3.0 ± 0.2 Ma). The results demonstrate the consistency in timing and conditions across the MCT at locations ∼650 km apart. If the present‐day Himalayan tectonic framework has not significantly changed since the Pliocene, the LHF duplex can be considered when attributing seismic events to particular faults. The MHT is undisputedly the significant factor in accommodating Himalayan seismic activity, but MCT footwall faults may explain some shallower hypocenters, without the need for unusual MHT geometries.

Capturing roaming molecular fragments in real time.

Since the discovery of roaming as an alternative molecular dissociation pathway in formaldehyde (H2CO), it has been indirectly observed in numerous molecules. The phenomenon describes a frustrated dissociation with fragments roaming at relatively large interatomic distances rather than following conventional transition-state dissociation; incipient radicals from the parent molecule self-react to form molecular products. Roaming has been identified spectroscopically through static product channel-resolved measurements, but not in real-time observations of the roaming fragment itself. Using time-resolved Coulomb explosion imaging (CEI), we directly imaged individual "roamers" on ultrafast time scales in the prototypical formaldehyde dissociation reaction. Using high-level first-principles simulations of all critical experimental steps, distinctive roaming signatures were identified. These were rendered observable by extracting rare stochastic events out of an overwhelming background using the highly sensitive CEI method.

Roaming dynamics in real time

Chemical Physics Roaming is distinct from conventional reaction channels because of the unusual geometries that chemical systems use to bypass the minimum energy pathway. It is a relatively new phenomenon that is usually determined in experiments through spectroscopic characterization of the roaming products. Using a combination of time-resolved Coulomb explosion imaging and quasiclassical trajectory analysis, Endo et al. report real-time observation of individual fragments of the prototypical reaction of deuterated formaldehyde (D2CO) dissociation as they roam on ultrafast time scales. They show that roaming not only occurs several orders of magnitude earlier than previously expected but also that it can terminate in a radical (D + DCO) rather than the well-known molecular (D2 + CO) product channel. Science , this issue p. [1072][1] [1]: /lookup/doi/10.1126/science.abc2960

Influence of the shape of a buoy on the efficiency of its dual-motion wave energy conversion

A procedure is proposed for the geometric design of the buoy of a single-body wave energy converter (WEC) based on the characteristics of incident waves. The effect of the buoy shape on its hydrodynamic performance and the absorption efficiency of WEC model is considered. The model absorbs the wave energy through the dual motion (heave and surge) of the buoy. In order to compare the dynamics of various buoys in waves, a set of requirements is proposed to create identical conditions. Three groups of buoy geometry, including conical, spherical and unusual geometry are considered. The changes in the hydrodynamic parameters of the buoy due to the buoy shape variations are studied to clarify the effect of these changes on the efficiency of the WEC model. The obtained results show that increasing a ratio of hydrodynamic coefficients of the buoy, increases the produced power regardless of the wave frequency. Also, an appropriate shape for the buoy can raise the WEC model performance from suboptimal mode to optimal mode and would also lead to a significant increase in the absorbed power and efficiency.

Behavior by design made possible by additive manufacturing: The case of a whistle-blower mechanical response

A pragmatic design strategy to achieve unusual mechanical responses in metal lattice structures is deployed. This strategy, referred to as behavior by design, is illustrated with an architectured material fabricated to provide a “whistle-blower” mechanical response under tensile loading. Struts with unusual geometries, e.g. dog-bone struts and corrugated struts, are assembled in parallel in a standard lattice unit-cell to obtain the targeted elasto-plastic behavior, here a “whistle-blower” behaviour. The design strategy benefits from the freedom provided by additive manufacturing.

Mid Infrared Tomography of Polymer Pipes

Mid-infrared signals in the 2–5 μm wavelength range have been transmitted through samples of polymer pipes, as commonly used in the water supply industry. It is shown that simple through-transmission images can be obtained using a broad spectrum source and a suitable camera. This leads to the possibility of tomography, where images are obtained as the measurement system is rotated with respect to the axis of the pipe. The unusual 3D geometry created by a source of finite size and the imaging plane of a camera, plus the fact that refraction at the pipe wall would cause significant ray bending, meant that the reconstruction of tomographic images had to be considered with some care. A result is shown for a thinning defect on the inner wall of a polymer water pipe, demonstrating that such changes can be reconstructed successfully.

Quantum-limit Chern topological magnetism in TbMn6Sn6.

The quantum-level interplay between geometry, topology and correlation is at the forefront of fundamental physics1-15. Kagome magnets are predicted to support intrinsic Chern quantum phases owing to their unusual lattice geometry and breaking of time-reversal symmetry14,15. However, quantum materials hosting ideal spin-orbit-coupled kagome lattices with strong out-of-plane magnetization are lacking16-21. Here, using scanning tunnelling microscopy, we identify a new topological kagome magnet, TbMn6Sn6, that is close to satisfying these criteria. We visualize its effectively defect-free, purely manganese-based ferromagnetic kagome lattice with atomic resolution. Remarkably, its electronic state shows distinct Landau quantization on application of a magnetic field, and the quantized Landau fan structure features spin-polarized Dirac dispersion with a large Chern gap. We further demonstrate the bulk-boundary correspondence between the Chern gap and the topological edge state, as well as the Berry curvature field correspondence of Chern gapped Dirac fermions. Our results point to the realization of a quantum-limit Chern phase in TbMn6Sn6, and may enable the observation of topological quantum phenomena in the RMn6Sn6 (where Ris a rare earth element) family with a variety of magnetic structures. Our visualization of the magnetic bulk-boundary-Berry correspondence covering real space and momentum space demonstrates a proof-of-principle method for revealing topological magnets.

Precision Timing in the CMS MTD Barrel Timing Layer With Crystal Bars and SiPMs

The Compact Muon Solenoid (CMS) detector at the European Council for Nuclear Research (CERN) Large Hadron Collider (LHC) is undergoing an extensive Phase II upgrade program to prepare for the challenging conditions of the high-luminosity LHC (HL-LHC). In particular, a new timing layer will measure minimum ionizing particles (MIPs) with a time resolution of ~30–40 ps and hermetic coverage up to a pseudorapidity of $\left |{ \eta }\right |=3$ . The precision time information from this detector will reduce the effects of the high levels of pileup expected at the HL-LHC and will bring new and unique capabilities to the CMS detector. This MIP Timing Detector (MTD) will consist of a central barrel timing layer (BTL) based on L(Y)SO:Ce crystals read out with silicon photomultipliers (SiPMs) and two end-caps instrumented with radiation-tolerant low-gain avalanche detectors (LGADs). With the goal of maximizing the detector performance within the stringent constraints of space, cost, and channel count, the BTL exploits elongated crystal bars, each read out with two SiPMs. This unusual geometry enables the instrumentation of large surfaces while minimizing the active area of the photodetectors and thus noise and power consumption. This article presents a summary of the research and development studies carried out to optimize this crystal-based technology and key beam test results in which the target time resolution of 30 ps has been achieved.

Synthesis, characterization and DFT studies of water stable Cd(II) metal–organic clusters with better adsorption property towards the organic pollutant in waste water

In this report, two water stable Cd(II) metal–organic clusters using slow evaporation method are designed and synthesized in order to explore for functional applications. The complexes are formulated as [Cd2(pda)2(H2O)6].(H2pda)2 (1) and [Cd4(Hpda)4(µ2-OH)2(Cl)2(H2O)6].2H2O (2) where H2pda = 2,6-pyridine dicarboxylic acid. The synthesized complexes show unusual hepta-coordinated geometry around the central metal ion. 1 is dinuclear while 2 is a tetranuclear discrete complex. The tetranuclear complex is the very first example of cadmium with H2pda ligand. The two complexes were characterized by various spectroscopic studies and with the help of single crystal technique the, structures of 1 and 2 was elucidated. Various non covalent interactions such as π-π and CH…π consolidate the network against water solubility. The metal–organic clusters exhibit various non-covalent interactions which were further verified by Hirshfeld surface analysis. The DFT calculations were also performed on both the complex which corroborate the electronic and spectral aspects of complexes. The stability of 1 and 2 was checked using the PXRD pattern of 1 and 2 after 10 hrs in water and it shows the identical pattern even after the 24 hrs. Further, the metal–organic clusters were checked for their adsorption property towards the cationic dye such as Rhodamine B. Out of the two complexes, only 2 shows better adsorption property due to its better stability in water. The mechanism of dye adsorption is also explored.

Unusual and Conventional Dative Bond Formation by s2 Lone Pair Donation from Alkaline Earth Metal Atoms to BH3, AlH3, and GaH3.

Using ab initio electronic structure methods with flexible atomic orbital basis sets, we examined the nature of the bonding arising from donation of an ns2 electron pair on an alkaline earth atom (Mg or Ca) into a vacant n'p orbital on the group 13 atom of BH3, AlH3, or GaH3. We also examined what happens when an excess electron is attached to form corresponding molecular anions. Although the geometries of MgBH3, MgAlH3, MgGaH3, and CaBH3 are found to be much as one would expect for datively bound molecules, CaAlH3 and CaGaH3 were found to have very unusual geometries in that their Al-H or Ga-H bonds are directed toward the Ca atom rather than away, as in the other compounds. Internal electrostatic Coulomb attractions between the partially positively charged Ca center and the partially negatively charged H centers were suggested as a source of these unusual geometries. The other novel finding is that the electron affinities (EAs) of all six M'-MH3 species lie in the 0.7-1.0 eV range, which is suggestive of ionic electronic structures for the neutrals even though the partial charges on the alkaline earth centers are as low as 0.3 atomic units. Partial positive charge on the alkaline earth atoms combined with substantial electron affinities of the BH3, AlH3, and GaH3 groups, but only when distorted from planar geometries, were suggested to be the primary contributors to the large EAs.

Anthracene-based Ni(II) thiosemicarbazones with novel intramolecular π–π stackings

Four new Ni(II) complexes were obtained from the reaction between anthracene-based thiosemicarbazones and inorganic metal salt. Structural investigation of the complexes using X-ray crystallography reveals unusual cis geometries driven by intramolecular π–π stackings between anthracenyl rings. Due to the novel interactions, the anthracenyl protons H1,8,2,7 are not observed and the imine proton is largely shifted in 1H NMR spectra. The UV–Vis and photoluminescent data clearly indicate strong perturbation of intramolecular π–π stackings on electronic structure of anthracenyl cores, namely broadening of absorption and emission bands.

Spherical trihedral metallo-borospherenes

The discovery of borospherenes unveiled the capacity of boron to form fullerene-like cage structures. While fullerenes are known to entrap metal atoms to form endohedral metallofullerenes, few metal atoms have been observed to be part of the fullerene cages. Here we report the observation of a class of remarkable metallo-borospherenes, where metal atoms are integral parts of the cage surface. We have produced La3B18– and Tb3B18– and probed their structures and bonding using photoelectron spectroscopy and theoretical calculations. Global minimum searches revealed that the most stable structures of Ln3B18– are hollow cages with D3h symmetry. The B18-framework in the Ln3B18– cages can be viewed as consisting of two triangular B6 motifs connected by three B2 units, forming three shared B10 rings which are coordinated to the three Ln atoms on the cage surface. These metallo-borospherenes represent a new class of unusual geometry that has not been observed in chemistry heretofore.