Unit Cell Dimensions Research Articles

Thermal expansion of minerals in the tourmaline supergroup

Abstract The thermal behavior of 15 natural tourmaline samples has been measured by X-ray powder diffraction from room temperature to ~930 °C. Axial thermal expansion is generally greater along the c crystallographic axis (αc 0.90–1.05 × 10–5/K) than along the a crystallographic axis and the symmetrically equivalent b axis (αa 0.47–0.60 × 10–5/K). Ferro-bearing samples show lower expansion along a than in other tourmalines. In povondraite the thermal expansion along the c axis is higher than in other tourmalines, whereas along a it is lower [αa = 0.31(2) and αc = 1.49(3) × 10–5/K]. Volume expansion in the tourmaline-supergroup minerals is relatively low compared with other silicates such as pyroxenes and amphiboles. Volume also exhibits a relatively narrow range of thermal expansion coefficients (1.90–2.05 × 10–5/K) among the supergroup members. An interpretation for the small changes in thermal expansion in a compositionally heterogeneous group like tourmaline is that all members, except povondraite, share a framework of dominantly ZAlO6 polyhedra that limit thermal expansion. Povondraite, with a framework dominated by ZFe3+O6 polyhedra, displays thermal expansion that is different from other members of the group. Unit-cell dimensions of tourmalines having significant Fe2+ deviate from linearity above 400 °C on plots against temperature (T); along with the resulting substantial reduction in unit-cell volume, these effects are likely the result of deprotonation/oxidation processes. Lithium-rich and Fe2+-free tourmalines deviate similarly at T > 600 °C. In Li- and Fe2+-free tourmalines, no such deviation is observed up to the highest temperatures of our experiments. It is not clear whether this is due to cation order-disorder over Y and Z sites that occurs during the highest temperature measurements, a phenomenon that is apparently inhibited (at least in the short term) in Li-free/Mg-rich samples. If so, this must occur at a relatively rapid rate, as no difference in unit-cell values was detected at 800 °C after heating in both one- and 12-h experiments on Na-rich rossmanite.

A new compact ultra-wideband frequency selective surface with angular stability and polarization independence for antenna radiation enhancement in microwave imaging application

A new compact, rudimental, uni layered frequency selective surface (FSS) is proposed to work in the commercial ultra-wideband (UWB) spectrum with its application in enhancing broadside radiation of an UWB antenna. The overall unit cell dimension (length × width × thickness) of the proposed UWB FSS is 0.15λL × 0.15λL × 0.016λL only where λL represents the wavelength corresponding to lowest band edge in the 3.04 to 10.88 GHz (∼112.6 %) spectrum with transmission coefficient less than −10 dB. Moreover, the proposed FSS provides certain degree of angular stability of 45° in both TE and TM planes of polarization. The proposed FSS is well suited for antenna gain augmentation as it offers linearly decreasing reflection phase profile. A compact ultra-wideband U-shaped CPW fed antenna with the dimension of 32 × 26 × 0.8 mm3 is designed that covers a bandwidth from 2.7 to 12.76 GHz (130 %). The proposed FSS is integrated with the U-shaped antenna to exhibit an improved and steady gain profile of 5.1–6.8dBi in the 2.82–12.92 GHz (128.34 %) impedance band. Maximum gain augmentation of 3.62 dBi is achieved at 9.5 GHz along with steady gain profile in the entire operating band of “antenna-FSS”, linear S21 response and flat group delay variations which implies the applicability of proposed antenna-FSS in various UWB communication purposes that comprise impulse radar, through wall imaging, microwave imaging, short range indoor communication etc. The applicability of UWB ‘antenna-FSS’ is established by ground coupling microwave imaging test in proximity of soil test bed where the fundamental characteristics of ‘antenna-FSS’ is found to be unaltered.

Structural study, Oxytetracycline electrochemical sensing property and molecular docking analysis of a novel synthesized non-centrosymmetric hybrid compound, [formula omitted

A novel non centrosymmetric organic–inorganic hybrid material bis(3-nitrotyrosine) bis(nitrate) (C9H11N2O5)2(NO3)2 denoted 3-NITY-Nitrate has been prepared at room temperature. The crystallographic study shows that the title compound crystallizes in the monoclinic system with P21 space group. Its unit cell dimensions are a = 13.8275 (10) Å, b = 5.7666 (4) Å, c = 15.5280 (12) Å, with V = 1211.11 (18) Å3 and Z = 4. The structure refined to a reliability R factor of 5.42 %. In the present investigation, the stability of crystal was assured by a network of N−H⋯O, O−H⋯O and C−H⋯O hydrogen bonds and through π⋯π and N−O⋯π interactions. The vibrational absorption bands were recorded by IR spectroscopy and have been identified in relation to the crystal structure of a made-up (C9H11N2O5)2(NO3)2 sample. The optical properties of the crystal were studied using UV–visible absorption and photoluminescence spectroscopy. A sensitive electrochemical sensor 3-NITY-Nitrate /GCE membrane was elaborated to detect Oxytetracycline in aqueous solutions. Oxytetracycline electrochemical behavior on the bare GCE and modified 3-NITY-Nitrate/GCE electrodes was studied by cyclic voltammetry. Analytical performance of the proposed sensor-based 3-NITY-Nitrate /GCE for OTC detection from 2*10−7 to 15*10−5 M was investigated using DPV. The limit of detection (LOD) was determined and the characteristics of this 3-NITY-Nitrate /GCE electrode such as reversibility, reproducibility and selectivity are discussed. From the molecular docking studies, it was observed that the organic ligand «3-nitrotyrosine» formed the bis(3-nitrotyrosine) bis(nitrate) (C9H11N2O5)2(NO3)2 fit well in the active site of cyclooxygenase-2.

Experimental and computational investigation of a novel organic cation hexachlorostannate (IV) material (C7H9N2O)2(SnCl6)

A novel organic–inorganic hybrid material (C7H9N2O)2(SnCl6) was obtained by synthetic reaction in aqueous solution. The crystallographic study shows that the investigated compound crystallizes in the triclinic system with P-1 space group. Its unit cell dimensions are a = 7.0859 (7) Å, b = 9.0553 (9) Å, c = 9.1442 (8) Å, a = 81.152(8) Å3, b = 87.126 (8) Å3, c = 67.977 (10) Å3 with V = 537, 43(25) and Z = 2.The three-dimensional framework and the stability of the crystal are insured by N−H⋯Cl, N−H⋯O and C−H⋯O hydrogen bonds and Cg⋯Cg (π⋯π) stacking. The vibrational absorption bands were recorded by IR spectroscopy and have been identified in relation to the crystal structure of a made-up (C7H9N2O)2(SnCl6) sample. The optical properties of the crystal were studied by using UV–visible absorption spectroscopy. The intermolecular interactions occurring in the crystal and their relative contributions in building the solid-state architecture, were quantified by using the three-dimensional Hirshfeld surfaces and two-dimensional fingerprint plots. In addition, the molecular geometries, vibrational frequencies of the compounds in the ground state have been performed using density functional theory (DFT) method, at B3LYP with 6-311g+(2d,2p) set for C, H, N, O, Cl atoms and LANL2DZ basis set for Sn atom.Topological AIM approaches and noncovalent interaction reduced density gradient (NCI-RDG) analyses and were pursued to generate a profound understanding of the structure-directing interactions in the compound. The NBO analysis was carried out to provide information about the delocalization of charge and energy density of atoms.

A Symmetrical Terahertz Triple-Band Metamaterial Absorber Using a Four-Capacitance Loaded Complementary Circular Split Ring Resonator and an Ultra-Thin ZnSe Substrate

In this research work, a symmetrical four-capacitance loaded complementary circular split ring resonator is proposed, which uses an ultra-thin Zinc Selenide (ZnSe) substrate to realize a low-profile triple-band metamaterial (MTM) perfect absorber for application in the terahertz (THz) frequency range. The electromagnetic properties of the proposed structure were calculated and investigated using the Finite Integration Technique (FIT). The proposed structure exhibited three highly absorptive (nearly perfect) peaks at the resonance frequencies of 15.68 THz, 37.48 THz, and 39.55 THz. Furthermore, the absorber was found to be insensitive to the polarization and incident wave angles, due to its symmetrical design. The effects of the conductor type, substrate thickness, unit cell dimension, resonator gap, and substrate type on the reflection and absorption spectra were investigated. To validate the numerical results, the proposed design was analyzed using High-Frequency Simulation Software (HFSS) and Advanced Design System (ADS). The surface current, electric field, and magnetic field distributions at the three-resonance frequency were analyzed. It was concluded that the overall performance of the proposed MTM structure was superior compared to those reported in the literature. The proposed design could be a good candidate for application in stealth technology, imaging, and thermal energy harvesting.

Crystal structures, hhirshfeld surfaces analysis, Infrared and Raman studies of organic-inorganic hybrid perovskite salts NH3(CH2)nNH3MnCl4 (n = 5, 6)

Layered 2D organic-inorganic hybrid perovskite (OIHs) of the diammonium series, 1,5 di-aminepentane tetrachloro manganate NH3(CH2)5NH3MnCl4 denoted C5MnCl and 1,6 di-aminhexane tetrachloro manganate NH3(CH2)6NH3MnCl4 (C6MnCl) were prepared by slow evaporation method, and structurally characterized by single crystal X-ray diffraction analysis. The C5MnCl hybrid crystallized in the orthorhombic non-centrosymmetric space group I212121 (Z ​= ​4) with parameters: a ​= ​7.1742 (3) Å, b ​= ​7.3817 (3) Å, c ​= ​23.9650 (10) Å, V ​= ​1269.13 ​Å3. While the C6MnCl crystallized in the centrosymmetric monoclinic system with P21/c (Z ​= ​4) space group, and unit cell dimensions: a ​= ​13.3738 (6) Å, b ​= ​7.3227 (3) Å, c ​= ​7.1886 (3) Å, β ​= ​93.673 (4)°. The both hybrid structures consist of organic dications ​+ ​NH3(CH2)nNH3+ (n ​= ​5, 6) extended in a zigzag structure while inorganic dianion manganate was coordinated by six Cl ions in distorted octahedra MnCl62− sharing two bridging chlorine atoms. The organic and inorganic layers were connected each other through N–H ….Cl hydrogen bonds to build cation-anion-cation structural cohesion. The Hirshfeld surface analyses are performed to compare the importance of hydrogen bonding contacts in the two hybrid compounds, where the H⋯Cl/Cl⋯H intercontacts are more important in C5MnCl rather in C6MnCl. Theoretical vibrational modes analyses are developed considering the structural data obtained on ​+ ​NH3(CH2)nNH3+ cations and MnCl42− anions to study the characteristic bands observed at room temperature in Infrared (400-4000 ​cm−1) and Raman (50-500 ​cm−1) spectra of the C6MnCl and C5MnCl compounds.

Saccoite, Ca2Mn+32F(OH)8⋅0.5(SO4), a new, microporous mineral from the Kalahari Manganese Field, South Africa

AbstractSaccoite, Ca2Mn3+2F(OH)8⋅0.5(SO4), is a new mineral found at the N'Chwaning III mine, Kalahari Manganese Field, Northern Cape Province, Republic of South Africa. It occurs as fillings of voids in hydrothermally altered manganese ore (comprising mostly of bixbyite and baryte). Further associated minor minerals are braunite, gypsum, chlorite, sturmanite and ettringite. Saccoite forms small needles, felted crystal masses or crusts. The new mineral is olive green, transparent, with white streak and vitreous lustre. No luminescence is observed. Saccoite is uniaxial (–) with refractive indices at 589(1) nm of ω = 1.705(5) and ɛ = 1.684(2). Pleochroism is distinct, i.e. bluish green (ω) and yellowish green (ɛ). The chemical composition was studied by means of an electron probe micro-analyser (EPMA) using wavelength-dispersive X-ray spectrometry (WDS). The empirical mineral formula is Ca2.06Mn3+1.78Cu0.10Mg0.07F0.97(OH)8.02(SO4)0.39. The unit-cell dimensions of saccoite (space group P4/ncc) are a = 12.834(3) Å, c = 5.622(2) Å, V = 926.0(4) Å3), and the calculated mass density is 2.73 g⋅cm–3. Saccoite exhibits a heteropolyhedral framework structure that is composed of edge- and corner sharing CaF2(OH)6 and M(OH)6 polyhedra (M = Mn3+ and Cu2+) with large channels along [001], which host disordered and only partially occupied groups, especially SO42–. The hydrogen atoms of the OH groups point into the channel to form hydrogen bonds with the channel anions. Ca–F distances are ~2.3 Å, the Ca–OH distances in the range of 2.44–2.58 Ǻ, and the M(OH)6 octahedron is strongly 4+2 Jahn-Teller distorted (4 × ~1.92 Å, 2 × 2.27 Å). The F atom is tetrahedrally coordinated to calcium atoms. The strongest lines in the powder X-ray diffraction pattern [d in Å (relative intensity) (hkl)] are: 9.0735 (35) (110), 4.5370 (95) (220), 4.0644 (20) (310), 3.0105 (100) (321), 2.8117 (20) (002), 2.7242 (75) (411), 1.9755 (35) (611), and 1.8142 (20) (550).

3-Phenyl-4-(prop-2-en-1-yl)-5-[(prop-2-en-1-yl)sulfanyl]-4H-1,2,4-triazole

1,2,4-Triazoles appear to be attractive substances due to their wide range of applications. Previously 3-phenyl-4-(prop-2-en-1-yl)-5-[(prop-2-en-1-yl)sulfanyl]-4H-1,2,4-triazole (Atr) has proven to be an effective precursor for us to prepare Cu(I)-π,σ-coordination compounds with nonlinear optical and magnetic properties. In this study, we present the structural characterization of Atr by a single-crystal X-ray diffraction method. The crystals are monoclinic, Sp.gr. P21, Z = 2, unit cell dimensions: a = 5.6967(3), b = 7.8045(3), c = 14.9327(7) Å, β = 91.113(4)°, V = 663.78(5) Å3 at 150 K. To analyze the intermolecular interactions in the crystal structure of Atr, a DFT computational study was also performed.

6-Amino-3-(prop-2-en-1-yl)-9H-purin-3-ium Tetracopper(I) Hexabromide: Synthesis and X-ray Structure Determination

6-Amino-3-(prop-2-en-1-yl)-9H-purin-3-ium tetracopper(I) hexabromide [(C5H5N5(C3H5))2Cu4Br6] (1) is synthesized in this paper. The title compound is characterized by Raman spectroscopy and single crystal X-ray diffraction: monoclinic, Sp.gr. P21/c, Z = 2, unit cell dimensions: a = 8.6870(3), b = 9.7447(2), c = 16.4418(4) Å, β = 100.681(3)°, V = 1367.72(7) Å3 at 150 K. The peculiarities of the metal coordination and distribution of weak interactions are analyzed. The significant role of hydrogen bonds in the construction of 1 crystal structure is shown.

Nano-bio effects: Interaction of ZnO and DNA-bases

In this study, we report on the complex formation and characterization of nano-bio conjugates synthesized by the sol–gel chemical method. The nano-bio conjugates, consisting of inorganic ZnO nanoparticles (NPs) and organic nitrogenous bases of DNA (Thymine and Cytosine), are investigated using electron microscopies, molecular vibrational analysis and X-ray spectroscopies. In this experimental investigation, we used two basic nitrogenous bases of DNA – Cytosine, and Thymine. The X-ray diffraction patterns of both ZnO NP and the nanoconjugate (NJ) reveal a highly phase pure ZnO structure with negligible changes in the unit cell dimensions. The Raman peaks due to the molecular vibration of C2=O7 and C4=O8 sites of Thymine and C=O and N-H sites in Cytosine are shifted due to the cation affinity after the interaction with ZnO NPs. The shifted XPS spectra towards higher binding energies of the NJ divulge the atomic level interaction between the DNA bases and ZnO NPs at the surface. Moreover, the formation of NJs reduces the surface defect states of the ZnO NPs and increases the fluorescence properties by quenching the oxygen vacancy concentration. Thus, the current study on the interfacial properties of organic–inorganic conjugate materials opens new frontiers for developing novel nano-bio conjugate materials and their integration for targeted drug delivery, biomolecular sensing and therapeutic tools medicine applications.

Experimental investigation on impact response of sandwich composites integrated with a novel 3D multi-layer stitched core

Impact damage resistance of the sandwich composites affects the structure reliability and crucially depends on the core. The weak junction of core unit-cell walls causes a catastrophic failure on sandwich composites under impact load. Stitching is an efficient and easy way to obtain the strengthened core unit-cells. In this study, the impact behavior of glass/epoxy face sandwich composites integrated with a novel 3D multi-layer stitched core were investigated. The peak forces and absorbed energy of sandwich composites were increased as the number of core layer increased. The increase in core layers and core dimensions caused more flexible sandwich composites. The core was more effective in the energy absorption mechanism of the sandwich composites than faces with the increased stitching density and decreased unit-cell size of core. The number of core layers, dimensions of core unit-cells and stitching density were found to be most important parameters for the impact failure of sandwich composites.

Influence of the Template Layer on the Structure and Ferroelectric Properties of PbZr0.52Ti0.48O3 Films.

The microstructure of the PbZr0.52Ti0.48O3 (PZT) films is known to influence the ferroelectric properties, but so far mainly the effect of the deposition conditions of the PZT has been investigated. To our knowledge, the influence of the underlying electrode layer and the mechanisms leading to changes in the PZT microstructure have not been explored. Using LaNiO3 (LNO) as the bottom electrode material, we investigated the evolution of the PZT microstructure and ferroelectric properties for changing LNO pulsed-laser deposition conditions. The explored deposition conditions were the O2 pressure, total pressure, and thickness of the electrode layer. Increasing both the O2 pressure and the thickness of the electrode layer changes the growth of PZT from a smooth, dense film to a rough, columnar film. We explain the origin of the change in PZT microstructure as the increased roughness of the electrode layer in relaxing the misfit strain. The strain relaxation mechanism is evidenced by the increase in the crystal phase with bulk LNO unit cell dimensions in comparison to the crystal phase with substrate-clamped unit cell dimensions. We explain the change from a dense to a columnar microstructure as a result of the change in the growth mode from Frank–van der Merwe to Stranski–Krastanov. The ferroelectric properties of the columnar films are improved compared to those of the smooth, dense films. The ability to tune the ferroelectric properties with the microstructure is primarily relevant for ferroelectric applications such as actuators and systems for energy harvesting and storage.

A digold(I) – Tetraalkynyl macrocycle with host-guest properties

In this contribution we wish to describe the synthesis and characterization of an anthraquinone-based dialkynyl ligand AQ-(OCH2CCH)2 (1, AQ = anthraquinone) and its coordination to Au(I) centers, to form a negatively charged tetraalkynyldigold macrocycle ([AQ-(OCH2CC)2Au]2(NPr4)2 (2)), capable to act as a host for positively charged species. X-Ray diffraction studies revealed that compound 1 crystalizes in the monoclinic crystal system, space group C2/c, with the unit cell dimensions a = 33.4705(19) Å, b = 6.8582(4) Å, c = 12.8850(7) Å, and β = 90.7990(10)°, with Z = 8. The supramolecular structure of 1 consists of ribbons running along the b axis of the unit cell, and it is supported by CC-H ··· O hydrogen bonds and π – π stacking interactions. Complex 2 crystalizes in the monoclinic crystal system, space group P21/c, with the unit cell dimensions a = 21.5515(9) Å, b = 15.3851(6) Å, c = 25.2615(10) Å, and β = 99.6730(10)°, with Z = 4. X-Ray diffraction investigations showed that the structure of 2 consists of two anthraquinone groups connected by two CC–Au–CC spacers, with an overall basket-like shape of the macrocycle. One tetrapropylammonium cation is positioned inside the macrocycle with two n-Pr groups being threaded through the cavity of the macrocycle, and the other two situated between the two anthraquinone moieties of the complex. This species is best described as an inclusion compound, formulated as {N[n-Pr]4+⊂22–}{N[n-Pr]4+}.

Crystal structure, phase transitions and Raman scattering in the new non‐centrosymmetric [(C3H7)4N]3Bi3Br12 compound

AbstractA novel tri‐tetrapropylammonium dodeca bromobismuthate (III) compound has been synthesized and studied by single‐crystal X‐ray diffraction, differential scanning calorimetry, and Raman spectroscopy as a function of temperature. At room temperature, the title compound crystalizes in noncentrosymmetric Cc space group which belongs to monoclinic crystal system. The unit cell dimensions are a = 11.083(6) Å, b = 19.100(6) Å, c = 31.146(3) Å, β = 98.42(0)°, and V = 6522.69(9) Å3. The crystal package is provided by electrostatic interactions and hydrogen bonds (C–H … Br). Intermolecular interactions present in the grown single crystal were analyzed by Hirshfeld surface and 2D fingerprint plot. The differential scanning calorimetry reveals two reversible phase transitions at 297 and 430 K. The values of the transition entropies suggest that the first is of an order–disorder type, while the second appears as a displacive one. The Raman versus temperature studies show that the vibrational states of tetrapropylammonium cations change markedly through the phase transitions. The most important changes are observed for two lines at 1034 and 1449 cm−1 (at room temperature) issued from the νs(N–C–C) + δs(C–N–C) and δs (CH3) of the cations. The spectral characteristics of these lines are analyzed and consistently described in the framework of an order–disorder model for the phase transitions.

Design and Analysis of Microstrip Patch Antenna properties with Split-Ring Resonator Metamaterial as Superstrate at mmWave Frequency

The Microstrip Patch antenna which is considered as low profile and easy to fabricate antenna incorporates drawbacks that include low gain and bandwidth. Using Metamaterials superstrate both bandwidth and the gain of patch antenna can be enhanced. This paper basically includes the study characteristics of rectangular patch antenna that is fed by microstrip line, with metamaterial as the two layers of superstrate is carried out at mmWave frequency ie 24GHz. The rectangular patch antenna is designed, that resonate at 24GHz, with copper as the radiating material put on Rogger 5880 substrate of 0.5mm thickness. The substrate dimension is taken to be 15mmx 15mm. The metamaterial structure exhibits negative permittivity and permeability at the same frequency as that of rectangular patch antenna ie at 24GHz. The substrate used for SRR structure design is Rogger 5880 of thickness 0.2mm. The unit cell dimension is 1.6mm x 1.6mm and the superstrate layer consists of a 9x9 SRR structure. Rectangular Patch characteristics are studied by placing the single layer and double layer of the superstrate at various distances (in mm). It is observed that placing a double superstrate layer with a gap of 1mm between them was placed at a distance of 1mm from the resonating rectangular patch antenna, making the antenna exhibit a multi-band feature along with an increase in the antenna gain. The Rectangular Patch antenna, SRR structure simulation is carried out in the CST simulation tool. Simulation results show that SRR characteristics are satisfied at 24GHz ie it behaves like a double negative structure and was verified using Matlab. The antenna shows multi-band resonance behavior at 24.033GHz, 25.36GHz, 25.285 GHz, 26.27 GHz when a double layer of 9x9 Split Ring Resonator is added above the radiating element. The gain offered by a single patch was 7.57dB and with the superstrate layer, the gain obtained was 9.01dB. The polarization component along the main lobe direction shows the cross-polarization component is found to be -85dB. The analysis of antenna with and without superstrate shows that there is improvement in gain and the multiband resonance can be achieved.

Verification of stability and unraveling the electronic and physical properties of bulk and (001)-surfaces of newly synthesized Ti2ZnX (X = C, N) MAX phases

MAX phase family has been extended by the addition of late transition metals at the A-site with the expectation of diverse functional properties. Here, we present our systematic density functional investigation on the thermodynamic and phonon stabilities, elastic properties, including elastic constants, elastic moduli and elastic anisotropy of newly synthesized Ti2ZnX (X = C, N) phases in comparison with conventional Ti2AlX (X = C, N). Due to the smaller size of N as compared to C, the unit cell dimension is reduced when C atoms are replaced by N atoms at the X-site. The Ti2ZnC and Ti2ZnN are stable at the equilibrium volume of 110.84 Å3 and 105.70 Å3. The thermodynamic, mechanical and dynamical stabilities are validated by estimating the formation energies, elastic constants and phonon dispersions, respectively. The elastic properties of Ti2ZnN are less anisotropic as compared to those of Ti2ZnC. To understand the thin-film characteristics in Ti2ZnX, the surface properties with (001)-terminated slabs are investigated. Both Ti2ZnX bulk and (001)-surfaces exhibit metal-like electronic structures. There is a strong covalent bonding between Ti-X and Ti-Zn atoms confirmed by the charge density map and Mulliken population analysis. Additional states are generated at the Fermi level (EF) due to the unusual d-p states hybridization between Ti and Zn atoms. The anisotropy in chemical bonding is confirmed by the cleavage energy difference between Ti-X and Ti-Zn. Here, Ti(X)-001 and Zn-001 terminations are stable surfaces; however, in terms of chemical potentials, Zn-001 termination is the most favourable in Ti2ZnX.

Morphological Evolution of Hydroxyapatite Nanoparticles, Synthesized via Modified Sol‐Gel and Microemulsion Technique, in Response to Their Synthesis Microenvironment

AbstractMethods for the synthesis and characterization of well‐dispersed nanostructured materials are widely explored for potential applications in various fields. Several challenges in synthesizing nanoparticles (NPs) with controlled morphology, narrow size distribution, and optimum stability are tested but the fundamental understanding of the growth of NP crystal structure leading to various morphologies still needs to be addressed. This study attempts to understand the role of the synthesis environment, i.e., solvents, stabilizing agents, and the surfactant concentration, that controls the crystal growth of the synthesized biocompatible hydroxyapatite nanoparticles resulting in different shapes and sizes. The lattice parameters, space group, interplanar spacing, and unit cell dimensions are calculated using the experimentally obtained powder diffraction patterns for the various NPs. Atoms are placed at random sites in the unit cell based on the collected crystallographic information, and a final atomic arrangement and subsequent morphological evolution are arrived at via local and global optimization.

Utilizing interdigital and supershape geometries for the design of frequency selective surfaces with high angular and polarization stabilities

In this research article, the superformula is used to design the geometry of a frequency selective surface (FSS) unit cell, which resembles the shapes found in nature. The designed shape of unit cell is like petals, which may take different form by varying the values of six parameters. The proposed FSS unit cell has both angular and polarization stabilities of incident wave. For the miniaturization of FSS and decrease of resonance frequency, interdigital capacitances (IDCs) are devised in the FSS structure, which do not deteriorate angular and polarization stabilities. The dimensions of the unit cell are 10 mm × 10 mm and the resonance frequency is specified as 3.5 GHz. An equivalent circuit is derived for the unit cell to evaluate its frequency responses. Its performance as the transmission coefficient is obtained by the equivalent circuit and full-wave simulation. The effects of variations of the geometrical dimensions of the FSS unit cell on its performance are studied. A prototype model of proposed FSS is fabricated and measured. The performance of its equivalent circuit, full-wave computer simulation results and measured data are compared and are shown to be in good agreement.

Chemical preparation, crystallographic characterization, vibrational study and thermal behavior of a new cyclotriphosphate CaNH4P3O9 · H2O

Chemical preparation, crystallographic characterization, IR studies and thermal behavior are presented for the new cyclotriphosphate CaNH4P3O9 · H2O and its anhydrous form CaNH4P3O9. CaNH4P3O9 · H2O was prepared by the method of ion exchange resin. CaNH4P3O9 · H2O crystallizes hexagonal, space group is P63 or P63/m or P6322 with the following unit-cell dimensions: a = b = 14.75(2) Å, c = 9.934(3) Å and Z = 8. The total dehydration of CaNH4P3O9 · H2O, between 70 °C and 180 °C, leads to its anhydrous form CaNH4P3O9. CaNH4P3O9 crystallizes in the monoclinic space group P21/n, Z = 4, with the following unit-cell dimensions: a = 7.446 Å, b = 12.46 Å, c = 10.050 Å, β = 90.11° and Z = 4. CaNH4P3O9 · H2O is stable until its melting point at 1050 °C. The thermal behavior of CaNH4P3O9 · H2O was investigated and interpreted by comparison with IR absorption spectrometry and X-ray diffraction experiments.

An organic hexamine p-nitrophenol crystal: Growth, optical, electrical, mechanical and density functional theoretical studies for nonlinear optical applications

Organic nonlinear optical hexamine p-nitrophenol (HMPN) crystal of dimension 19 × 15 × 9 mm3 was grownup by slow evaporation technique at uniform temperature. Unit cell dimensions are identified through XRD analysis. Both theoretical and experimental researches are briefly presented in order to draw a conclusion on UV spectroscopic, electronic, and nonlinear optic-response features of HMPN. Optical absorption and transmittance of HMPN are investigated through UV–vis–NIR spectroscopy. The powder second harmonic generation (SHG) efficiency of HMPN is 4.57 times greater to standard KDP. The first hyperpolarizability for SHG of HMPN molecule was evaluated on optimized geometry with B3LYP 6–311++G (d, p). Dielectric constant, impedance, ac conductivity and electric modulus as function of frequency at various temperatures were studied. Mechanical properties were studied by Vickers micro hardness test. Molecular electrostatic potential (MEP) technique is used for identifying electrophilic and nucleophilic sites.