Space Group Pna21 Research Articles

(1,2,5,6-η)-Cycloocta-1,5-diene]bis(thiocyanato-κS)platinum(II)

In the title complex, [Pt(SCN)2(C8H12)], the PtII ion lies in a square-planar coordination geometry defined by the mid-points of the two π-coordinated double bonds of cycloocta-1,5-diene and two S-bound SCN− anions. The complex is disposed about a mirror plane passing through the Pt atom and the SCN− ligands, and bisecting the cycloocta-1,5-diene molecule. The room-temperature crystal structure of the title complex was previously reported in the orthorhombic space group Pna21 [Musitu & Garcia-Blanco (1984). Acta Cryst. A40, C101]. The low-temperature structure presented herein represents a different (higher symmetry) orthorhombic space group Pnma whereby the PtII atom lies on a mirror plane, lacking in the earlier study.

Crystal and Molecular Structures of Five 3D Organic Salts from 2,6-Dimethylaniline and Organic Acids

Five crystalline organic acid-base salts [(HL)·(dnsa−), L = 2,6-dimethylaniline, dnsa− = 3,5-dinitrosalicylate] (1), [(HL+)·(4-Hnpta−), 4-Hnpta− = 4-nitrophthalate] (2), [(HL)2·(nds)·(H2O)2, nds = 1,5-naphthalenedisulfonate] (3), [(HL)·(dnb)·(Hdnb), dnb = 3,5-dinitrobenzoate, Hdnb = 3,5-dinitrobenzoic acid] (4) and [(HL)·(dca), dca = dichloroacetate] (5) from 2,6-dimethylaniline and organic acids were prepared and characterized by XRD analysis, IR, mp and elemental analysis. Compound 1 adopts the triclinic, space group Pī, with a = 7.6261(6) A, b = 8.3429(8) A, c = 13.1147(12) A, α = 91.3610(10)o, β = 102.755(2)o, γ = 102.597(2)o, V = 791.96(12) A3, Z = 2. Compound 2 belongs to the monoclinic, space group P2(1)/c, with a = 14.2552(15) A, b = 8.1436(8) A, c = 14.5708(13) A, α = 90°, β = 113.795(2)o, γ = 90°, V = 1547.7(3) A3, Z = 4. Compound 3 crystallizes in the monoclinic, space group P2(1)/c, with a = 8.4784(7) A, b = 17.4798(15) A, c = 9.1119(8) A, α = 90°, β = 99.742(2)o, γ = 90°, V = 1330.9(2) A3, Z = 2. Compound 4 has orthorhombic, space group Pna2(1), with a = 24.5029(19) A, b = 7.5322(9) A, c = 26.665(2) A, α = 90°, β = 90°, γ = 90°, V = 4921.3(8) A3, Z = 8. Compound 5 crystallizes in the monoclinic, space group C2/c, with a = 19.8970(17) A, b = 11.1850(11) A, c = 13.1590(12) A, α = 90°, β = 123.408(3)o, γ = 90°, V = 2444.6(4) A3, Z = 8. For 1 it was the relatively weak phenol that has ionized, different from 2 to 5. All supramolecular architectures of 1–5 involve N–H⋯O H-bonds as well as CH3⋯O interactions. The other noncovalent interactions (CH⋯O, CH⋯Cl, O⋯C, O⋯N, O⋯O, Cl⋯Cl, C⋯π, O⋯π, CH3⋯π and π⋯π) in the crystal packing were also ascertained. These weak interactions combined, all compounds displayed 3D framework structures. In the five prepared supramolecular assemblies there are plenty of weak bonding interactions such as directional H-bonds of N–H⋯O, O–H⋯O, O–H⋯S, O–H⋯N and noncovalent bonds of CH⋯O, CH3⋯O, CH⋯Cl, O⋯C, O⋯N, O⋯O, Cl–Cl, C⋯π, O⋯π, CH3⋯π, and aryl⋯aryl interactions. All compounds displayed the 3D framework structures

Ion exchange synthesis of Ag+ incorporated LiAlO2 and its application in photodegradation of organic dyes

The present work aimed at the synthesis, characterization and photodegradation studies of visible light active silver ion (Ag+) incorporated LiAlO2 catalyst. Ethylene glycol assisted sol–gel method was adopted to prepare LiAlO2 at 700 °C. AgAlO2 was synthesized by cation exchange of LiAlO2 by the solid-state method at 300 °C. The structural and optical properties were characterized by powder X-ray diffraction and UV–Vis diffuse reflectance spectroscopy respectively. The scanning electron microscopy (SEM) provided the morphological information of as-prepared samples. LiAlO2 and AgAlO2 were crystallized in a tetragonal lattice (space group P412121) and orthorhombic (space group Pna21) respectively. The bandgap energy of the samples was determined by the Kubelka–Munk (KM) plot. SEM measurements revealed the flower-like hierarchical shape particles. The photocatalytic properties of these samples were evaluated by the degradation of methylene blue and rhodamine B dyes. The mechanistic degradation pathway of RhB was studied using radical quenchers. The rate of recombination of the charge carriers during photocatalysis was discussed.

Synthesis of polyoxometalates, copper molybdate (Cu3Mo2O9) nanopowders, for energy storage applications

Synthesis of polyoxometalates (Cu3Mo2O9 nanopowders) was obtained by using solvothermal method and confirmed by X-ray diffraction pattern, with orthorhombic crystalline structure belonging to the space group Pna21(33). Further, the synthesized Cu3Mo2O9 nanopowders were analyzed by using Raman, infrared, and photoluminescence studies. X-ray photoelectron spectroscopy study explained the oxidation states of Mo-3d, Cu-2p, and O-1s in Cu3Mo2O9 nanopowders. Field emission scanning electron microscopy images clearly revealed the formation of nanostructure randomly oriented to form an interconnected rout, which emerged as a good candidate for storing more charges at the surface of Cu3Mo2O9 nanopowders. The electrochemical studies, such as cyclic voltammetry, electro impedance analysis, and galvanostatic charging–discharging studies, were used to analyze its electrochemical properties. To ensure the stability of Cu3Mo2O9 nanopowders, continuous charging and discharging studies were conducted for 1000 cycles at a current density of 5 A g−1 and it exhibited good stability over a large number of cyclic studies with capacity retention of 99.2% after the first 500 cycles.

Directional Intermolecular Interactions for Precise Molecular Design of a High- Tc Multiaxial Molecular Ferroelectric.

Quasi-spherical molecules have recently been developed as promising building blocks for constructing high-performance molecular ferroelectrics. However, although the modification of spherical molecules into quasi-spherical ones can efficiently lower the crystal symmetry, it is still a challenge to precisely arouse a low-symmetric polar crystal structure. Here, by introducing directional hydrogen-bonding interactions in the molecular modification, we successfully reduced the cubic centrosymmetric Pm3̅ m space group of [quinuclidinium]ClO4 at room temperature to the orthorhombic polar Pna21 space group of [3-oxoquinuclidinium]ClO4. Different from the substituent groups of -OH, -CH3, and ═CH2, the addition of a ═O group with H-acceptor to [quinuclidinium]+ forms directionally N-H···O═C hydrogen-bonded chains, which plays a critical role in the generation of polar structure in [3-oxoquinuclidinium]ClO4. Systematic characterization indicates that [3-oxoquinuclidinium]ClO4 is an excellent molecular ferroelectric with a high Curie temperature of 457 K, a large saturate polarization of 6.7 μC/cm2, and a multiaxial feature of 6 equiv ferroelectric axes. This work demonstrates that the strategy of combining quasi-spherical molecule building blocks with directional intermolecular interactions provides an efficient route to precisely design new eminent molecular ferroelectrics.

Nonlinear optical organic-inorganic crystals: synthesis, structural analysis and verification of harmonic generation in tri-(o-chloroanilinium nitrate).

The structural and nonlinear optical properties of a new anilinium hybrid crystal of chemical formula (C6H7NCl+·NO3-)3 have been investigated. The crystal structure was determined from single-crystal X-ray diffraction measurements performed at a temperature of 100 K which show that the compound crystallizes in a noncentrosymmetric space group (Pna21). The structural analysis was coupled with Hirshfeld surface analysis to evaluate the contribution of the different intermolecular interactions to the formation of supramolecular assemblies in the solid state that exhibit nonlinear optical features. This analysis reveals that the studied compound is characterized by a three-dimensional network of hydrogen bonds and the main contributions are provided by the O...H, C...H, H...H and Cl...H interactions, which alone represent ∼85% of the total contributions to the Hirshfeld surfaces. It is noteworthy that the halogen...H contributions are quite comparable with those of the H...H contacts. The nonlinear optical properties were investigated by nonlinear diffuse femtosecond-pulse reflectometry and the obtained results were compared with those of the reference material LiNbO3. The hybrid crystals exhibit notable second (SHG) and third (THG) harmonic generation which confirms its polarity is generated by the different intermolecular interactions. These measurements also highlight that the THG signal of the new anilinium compound normalized to its SHG counterpart is more pronounced than for LiNbO3.

Nickel(II) complexes with tripodal NNN ligands as homogenous and supported catalysts for ethylene oligomerization

Four new coordination compounds of nickel (II) with derivatives of N,N-bis(pyrazol-1-ylmethyl)propylamine were synthesized; their composition and structure were confirmed with IR-spectroscopy and elemental analysis. The structures of products 13 and 15 were unambiguously established in an X-ray diffraction study. Compounds 13 and 15 crystallize in the orthorhombic space groups Pna21 and P212121 correspondingly and represent a monomeric octahedral nickel complexes, that are typical for tridentate scorpion-type ligands. New method for immobilization of nickel complexes with derivatives of N,N-bis(pyrazol-1-ylmethyl)propylamine on silica gel modified with aminopropyl groups was proposed. The EXAFS/XANES analysis indicated that Ni atom in the supported complexes adopt almost octahedral geometry, being partly surrounded by nitrogen atoms from organic ligand and partly grafted to silica surface through silanol groups, with Br− in outer coordination sphere. Both the original and the supported complexes, when activated with Et2AlCl or Et3Al2Cl3, catalyze ethylene oligomerization with the predominant formation of butene isomers. Generally, the immobilized complexes show higher activity and better selectivity towards 1-butene formation.

Studies on optical, electrical, mechanical and theoretical investigation of 4-nitro-benzoic acid (3-ethoxy-2-hydroxy-benzylidene)-hydrazide: A novel Schiff base organic NLO material

New organic non-centrosymmetric Schiff base material 4-Nitro-benzoic acid (3-ethoxy-2-hydroxy-benzylidene)-hydrazide was synthesized and grown as single crystal by slow evaporation solution growth technique. Single crystal X-ray diffraction reveals the noncentrosymmetric nature of the grown crystal with space group Pna21. The nonlinear efficiency of the grown material was studied by Kurtz-Perry powder technique and found to be 0.7 times that of KDP. The photoluminescence emission of the grown crystal shows emission at 360 nm. The mechanical stability of the crystal was examined by Vicker's microhardness study and the yield strength of the material was calculated. Low dielectric constant at higher frequencies was observed from dielectric measurements. Reduction in charge carriers when the sample was illuminated by halogen lamp proves the negative photoconductivity of the sample. In addition, quantum chemical calculations were carried out using density functional theory for the NEH molecule optimized at B3LYP/6-31 + G (d, p) basis set to calculate its frontier molecular orbital, electrostatic potential and Mulliken charge analysis.

Second and third order nonlinear optical studies of a novel thiophene substituted chalcone derivative

A noncentrosymmetric chalcone derivative (E)-1-(thiophen-2-yl)-3-(3, 4, 5-trimethoxyphenyl) prop-2-en-1-one (TTMP) was synthesized using Claisen Schmidt condensation approach and single crystals were grown using slow evaporation method. The grown TTMP crystals crystallizes in orthorhombic structure with Pna21 space group. The intermolecular interactions of the TTMP crystals were envisioned by Hirshfeld surface analysis (HSA). Further, the structural conformations of the crystal were carried out by using 1H NMR, FTIR, and FT-Raman spectral analysis. The UV–Vis–NIR spectrum of the sample clearly shows the prime transparency in the entire visible and near infrared region. Thermal studies (TG/DTA/DSC) of the TTMP sample shows excellent thermal stability and phase transition and also noticed that crystal was most stable up to 152.65 °C. The second harmonic generation efficiency was obtained for the crystals using Nd:YAG laser and is to be 1.93 times that of urea. The third order nonlinear absorption coefficient (β), nonlinear refractive index (n2), third-order nonlinear susceptibilities (χ (3)), second order hyper polarizability (γh) and optical limiting thresholds were determined by Z-scan technique using the Diode-Pumped Solid State (DPSS) Continuous Wave (CW) laser. The results suggest that the TTMP molecules are promising materials for optoelectronic device applications.

The X-ray Structure of 4-Aminobenzyl alcohol (4-Aminophenylmethanol)

A second polymorph of 4-aminobenzyl alcohol [orthorhombic, a = 8.95051(15), b = 5.8248(1), c = 12.1645(2) Å, space group Pna21] shows a “herringbone” structure with stacks of hydrogen-bonded molecules when viewed down the b-axis.Graphical A new polymorph of 4-aminobenzyl alcohol adopts a “herringbone” structure with stacks of hydrogen bonded molecules viewed down the b-axis.

Synthesis, structure elucidation, spectroscopic analysis, thermal and NLO properties of A new piperidine derivative – (4-Methylphenyl) (4-methylpiperidin-1-yl) methanone

A new organic nonlinear optical material (4-methylphenyl) (4-methylpiperidin-1-yl) methanone(MPMPM) was synthesized by slow evaporation method using Schotten-Boumann condensation reaction. A single crystal XRD study shows that the compound crystallizes in orthorhombic crystal system with a space group of Pna21 with lattice parameters a = 20.272(13), b = 7.188(5), c = 8.471(6) Å and V = 1234.46(15) Å3. Structure of the compound was elucidated with SHELXS 97 and SHELXL 14. The grown crystal was characterized by FT-IR, NMR, UV and PL spectral analysis. The band gap energy calculated using UV–Vis spectral data is 4.1972 eV. Thermal analysis TG/DTA was carried out in the temperature range 30–320 °C. Kinetic and thermodynamic parameters were determined using the data obtained from the thermogram for the decomposition process by Coats-Redfern relation. The second harmonic generation (SHG) efficiency of MPMPM is 1.074 times that of KDP crystals and is suitable for opto-electronic applications.

New data on cafarsite: reinvestigation of its crystal structure and chemical composition

The crystal structure of cafarsite from Wanni glacier  Monte Cervandone was re-investigated by single crystal X-ray diffraction (space group Pn-3, R1 = 0.022) and new electron-microprobe analyses. REE (mainly Ce and Y) were found to substitute Ca. A new anion site, four-coordinated by Ca, was located by difference Fourier analysis and refined with F scattering factors. Two octahedral sites (Ti1 and Fe2) are occupied by mainly Ti and Fe3+, replacing each other whereas the octahedral site Mn1 hosts Mn2+ and Fe2+. The new structure refinements and chemical analyses lead to the simplified chemical formula (Ca7.8Na0.8Mn0.5REE0.4)∑9.5(Ti3.9Fe3+2.1Fe2+0.9Mn2+0.1) ∑7(AsO3)14F0.5. According to our findings, there is no evidence of neither H2O nor OH in the structure. In contrast to the original study by Edenharter et al. (1977), the structure has no significant cation vacancies and is based on 14 AsO3 groups pfu and not on 12 AsO3 as previously suggested.

Crystal growth and characterization of 1,3,5-triphenylbenzene organic scintillator crystal

Abstract 1,3,5-triphenylbenzene (TPB) crystal cylinders of 23 × 13 mm were successfully achieved out of an optimized unidirectional temperature gradient method. The Powder X-ray diffraction confirms that the grown crystal belongs to orthorhombic crystal system with non-centrosymmetric space group (Pna21). The crystalline structural perfection of the grown crystal was examined by high resolution X-ray diffraction analysis. FTIR and Raman studies aid to identify the expected molecular structure and the basic functional group of vibrational modes. The UV–Visible spectral analysis was carried out and the cut-off wavelength was observed at 228 nm. The Photoluminescence and The X-ray induced luminescence spectra were recorded and found the emission around 355 nm. The structural defects were analyzed through chemical etching micrographs. Pulse height spectra and the Scintillation decay time measurement also carried out under γ-rays from 137Cs source. The thermal diffusivity, conductivity and effusivity data from photoacoustic spectroscopy supports the application of this material for scintillation.

Crystal growth, physical properties, and theoretical investigation on organic acentric single crystal towards efficient second-order NLO applications: Triphenylguanidine

A novel organic nonlinear optical crystal Triphenylguanidine (TPG) was grown by the solvent evaporation method. Single-crystal X-ray diffraction (XRD) studies showed that the TPG compound crystallizes in orthorhombic crystal system with Pna21 space group and the corresponding lattice planes of reflections were indexed using powder XRD studies. Fourier transform infrared and Fourier transform Raman studies revealed the presence of various functional groups in the TPG crystal. The molecular structure of TPG was also confirmed using the NMR studies. UV–Vis studies validate the aptness of TPG crystal towards nonlinear optical applications. TPG crystal shows blue emission from photoluminescence studies. The mechanical stability of the grown crystal was identified using Vickers microhardness studies. Dielectric studies were carried out as a function of frequency at room temperature. Powder SHG effective nonlinearity of TPG crystal is about 2.3 times that of standard KDP. The thermal stability of TPG crystal was investigated by the TG-DTA studies. Using Gaussian 03 program the HOMO–LUMO energy gap and first-order hyperpolarizability value for TPG molecule were calculated. The calculated first-order hyperpolarizability value of TPG molecule is 17 times that of urea.

Synthesis, Structure, and Characterization of Defect‐free [Hf6(μ3‐O)4(μ3‐OH)4(C4H2O4)6] (Hf‐UiO‐66‐Fum)

The reaction of HfCl4 with fumaric acid (C4H4O4, H2Fum) in a DMF/HCOOH solvent mixture at 120 °C for 24 h results in the formation of a defect‐free sample of Hf‐UiO‐66‐Fum with UiO‐66 structure type. Treatment of the (as)‐synthesized sample in boiling ethanol followed by a thermal treatment at 70 °C leads to a sample of composition [Hf6(μ3‐O)4(μ3‐OH)4(Fum)6]·18H2O·2EtOH. In the crystal structure the hexanuclear clusters {Hf6(μ3‐O)4(μ3‐OH)4} are twelve‐fold connected by C4H2O42– ions to form the framework with the fcu topology. This cluster connectivity was confirmed by a combination of characterization techniques methods, i.e. CHN analyses, N2 sorption as well as 1H‐NMR spectroscopic and thermogravimetric measurements. The MOF shows a thermal stability of T = 390 °C, a specific BET surface area of 389 m2·g–1 and a water uptake of 204 mg·g–1. The crystal structure was determined from powder X‐ray diffraction (PXRD) data, employing the Rietveld method. The compound crystallizes in the cubic space group Pn3 and is isostructural to Zr‐UiO‐66‐Fum. Only a small increase of the lattice parameter a from 17.8309(4) to 17.87978(14) Å is observed.

Tuning the Anomeric Effect in Sulfamide with Superacids.

This study shows that the anomeric effect (negative hyperconjugation) that arises in sulfamide, as a result of the relatively short S-N bonds, can be tuned by the utilization of superacidic media. Sulfamide was reacted in binary superacidic systems XF/MF5 (M=As, Sb; X=H, D) and HF/BF3 . The colorless salts formed, [X2 NSO2 NX3 ]+ [MF6 ]- and [H2 NSO2 NH3 ]+ [BF4 ]- were characterized by low-temperature vibrational spectroscopy. In the case of [H2 NSO2 NH3 ]+ [BF4 ]- , a single crystal X-ray diffraction study was performed. The salt crystallizes in the monoclinic space group P21 /c with four formula units per unit cell. An exclusive N,N'-diprotonation was observed in the superacidic system HF/SbF5 when using several equivalents of the Lewis acid. Low-temperature vibrational spectra as well as a single-crystal X-ray structure of [H3 NSO2 NH3 ]2+ 2 [SbF6 ]- ⋅2 HF are reported. The salt crystallizes in the orthorhombic space group Pna21 with four formula units per unit cell. Upon mono- or diprotonation of sulfamide, remarkable structural changes of the sulfur-nitrogen bond lengths were observed. Herein, these changes are discussed together with quantum chemical calculations.

Optical, structural characterization and dielectric relaxation of [C2H5NH3]2ZnCl4 compound

ABSTRACTThe new organic-inorganic compound [C2H5NH3]2ZnCl4 has been grown by the slow evaporation at room temperature. The zero-dimensional (0-D) structure for this compound was determined by the single X-ray diffraction. It crystallizes at room temperature in the non-centrosymmetric space group Pna21 and consists of ethylammonium cations [C2H5NH3]+ and [ZnCl4]2− tetrahedra anions. That is interconnected by means of hydrogen bonding contacts N-H···Cl. The molecular geometry and vibrational frequencies of [ZnCl4]2− and [C2H5NH3]+ in the ground state was calculated using density functional method (B3LYP) with 6–31G(d) and 6–311G (d,p) basis set. The optimized geometric bond lengths and bond angles, obtained by using B3LYP/6–311G (d,p), show the best agreement with the experimental data. The optical absorbance was measured in order to deduce the absorption coefficient α, optical band gap Eg. The optical band gap is determined by extrapolating the plotted graph of (αhυ)1/2 vs. (hυ). The large value of indirect optical band gap energy indicates the insulating nature of this material. Moreover, the extinction coefficient, refractive index and the dielectric permittivity of [C2H5NH3]2ZnCl4 compound were calculated and the results are discussed. The evolution of the dielectric loss as a function of frequency revealed a distribution of relaxation times, probably ascribed to the reorientational dynamics of alkyl chains in this compound, and then analyzed with the Cole–Cole formalism.

Syntheses and Crystal Structures of Mn(II), Ni(II) and Cu(II) Coordination Compounds Assembled by Maleato and Dimethyl-2,2′-bipyridines

Three complexes: {[Mn(H2O)(mal)(5dmb)·H2O}n] (1); [Ni2(H2O)6(mal)2(4dmb)2]·3H2O (2); [Cu2(mal)2(4dmb)2]·3H2O (3); where mal = maleato, 4dmb = 4,4′-dimethyl-2,2′-bipyridine, and 5dmb = 5,5′-dimethyl-2,2′-bipyridine; have been synthesized, using self-assembly solution reactions at ambient conditions. Crystallographic studies show that 1 crystallizes in an orthorhombic system, space group Pna21, with a = 17.4067(4) A, b = 11.9672(2) A, c = 8.2075(2) A; V = 1709.70(6) A3. Complex 2 has a monoclinic system, space group C2/c, with a = 21.206(8) A, b = 7.523(3) A, c = 25.399(10) A; β = 109.755(8)°; V = 3813(2) A3. Complex 3 crystallizes in a monoclinic system, space group C2/c, with a = 14.6976(12) A, b = 11.3849(10) A, c = 22.1638(18) A; β = 101.2998(17)°; V = 3636.8(5) A3. Complex 1 is a one-dimensional (1D) polymer, where the Mn centers are six-coordinated in a distorted octahedral geometry. 2 is a dinuclear complex, generated by supramolecular interactions, where Ni ions are six-coordinated in a distorted octahedral geometry. 3 is a dinuclear complex with five-coordinated Cu ions having a distorted square pyramidal geometry. All three complexes exhibit hydrogen bonding interactions, which generate 2D supramolecular structures in 1 and 2, whereas in complex 3 a 3D supramolecular array is formed. These novel complexes prove that the self-assembly of a dicarboxylate ligand (mal) with three different first-row transition metals, can afford coordination compounds with diverse structural characteristics and dimensionality, which can be attributed to the different ligand coordination modes and the coordination properties of the employed metals. Divergent coordination compounds of three different transition metals have been obtained due to the versatility in the coordination modes of maleato ligand.

Synthesis and Characterization of the First Tin Fluoride Borate Sn3 [B3 O7 ]F with Second Harmonic Generation Response.

The new non‐centrosymmetric tin fluoride borate Sn3[B3O7]F was synthesized hydrothermally, and was characterized by single‐crystal and powder X‐ray diffraction, vibrational spectroscopy, DFT calculations, second harmonic generation (SHG) measurements, thermogravimetry, and differential scanning calorimetry. Its SHG response is about 12 times that of quartz. The compound crystallizes in the non‐centrosymmetric orthorhombic space group Pna21 with lattice parameters a=922.4(2), b=769.8(4), and c=1221.9(6) pm (Z=4). Characteristic for the structure are isolated B3O7 moieties, consisting of two corner‐sharing BO3 units and one BO4 tetrahedron. These occupy half of the octahedral voids of a slightly distorted hexagonal closest packing of Sn2+ atoms, with [SnF]+ units in the other half of the octahedral voids. Sn3[B3O7]F is transparent over a wide spectral range with a UV cut‐off edge at about 263 nm.

X-ray single-crystal structural characterization of Na2MgSiO4 with cristobalite-type structure synthesised at 22 GPa and 1800 °C

Na 2 MgSiO 4 is a mineralogical phase known in the literature as N2MS and reported in several high-pressure experiments (13.6 P PT Na 2 MgSiO 4 is known, a structural study of the phase recovered in high-pressure experiments has not been done yet. Here we present a chemical and structural study of a crystal of Na 2 MgSiO 4 synthesised in the model system Na 2 MgSiO 4 –Mg 2 SiO 4 at 22 GPa and 1800 °C. The compound was found to crystallize with the orthorhombic cristobalite-type structure previously described at room conditions, space group Pna 2 1 , with lattice parameters a = 10.8193(8), b = 5.2702(3), c = 7.0598(4) A, V = 402.55(4) A 3 , and Z = 4. The structure was refined to R 1 = 0.0184 using 644 observed reflections [ F o > 4σ( F o )] and 73 parameters. The unit-cell of the phase studied here is nearly identical to that of Na 2 MgSiO 4 synthesised at room conditions, thus indicating that it likely relaxed during the pressure release occurring during quenching.