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1,063 results on '"Dinnebier, Robert E."'

272. Na2IrIVCl6: Spin–Orbital-Induced Semiconductor Showing Hydration-Dependent Structural and Magnetic Variations

Author

Bao, Song-Song, Wang, Di, Huang, Xin-Da, Etter, Martin, Cai, Zhong-Sheng, Wan, Xiangang, Dinnebier, Robert E., and Zheng, Li-Min

Abstract

Iridium(IV) oxides have gained increased attention in recent years owing to the presence of competing spin–orbit coupling and Coulomb interactions, which facilitate the emergence of novel quantum phenomena. In contrast, the electronic structure and magnetic properties of IrIV-based molecular materials remain largely unexplored. In this paper, we take a fresh look at an old but puzzling compound, Na2IrCl6, which can be hydrated to form two stable phases with formulas Na2IrCl6·2H2O and Na2IrCl6·6H2O. Their crystal structures are well illustrated based on X-ray powder diffraction data. Magnetic studies reveal that Na2IrCl6and Na2IrCl6·2H2O are canted antiferromagnets with ordering temperatures of 7.4 and 2.7 K, respectively, whereas Na2IrCl6·6H2O is paramagnetic down to 1.8 K. First-principle calculations on Na2IrCl6reveal a Jeff= 1/2 ground state, and the band structures show that Na2IrCl6is a spin–orbital-induced semiconductor with an indirect gap of about 0.18 eV.

Published
2018
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273. Structures, Thermodynamic Relations, and Magnetism of Stable and Metastable Ni(NCS)2Coordination Polymers

Author

Neumann, Tristan, Ceglarska, Magdalena, Germann, Luzia S., Rams, Michał, Dinnebier, Robert E., Suckert, Stefan, Jess, Inke, and Näther, Christian

Abstract

Reaction of Ni(NCS)2with 4-aminopyridine in different solvents leads to the formation of compounds with the compositions Ni(NCS)2(4-aminopyridine)4(1), Ni(NCS)2(4-aminopyridine)2(H2O)2(2), [Ni(NCS)2(4-aminopyridine)3(MeCN)]·MeCN (3), and [Ni(NCS)2(4-aminopyridine)2]n(5-LT). Compounds 1, 2, and 3form discrete complexes, with octahedral metal coordination. In 5-LTthe Ni cations are linked by single thiocyanate anions into chains, which are further connected into layers by half of the 4-aminopyridine coligands. Upon heating, 1transforms into an isomer of 5-LTwith a 1D structure (5-HT), that on further heating forms a more condensed chain compound [Ni(NCS)2(4-aminopyridine)]n(6) that shows a very unusual chain topology. If 3is heated, a further compound with the composition Ni(NCS)2(4-aminopyridine)3(4) is formed, which presumably is a dimer and which on further heating transforms into 6via 5-HTas intermediate. Further investigations reveal that 5-LTand 5-HTare related by enantiotropism, with 5-LTbeing the thermodynamic stable form at room-temperature. Magnetic and specific heat measurements reveal ferromagnetic exchange through thiocyanate bridges and magnetic ordering due to antiferromagnetic interchain interactions at 5.30(5) K and 8.2(2) K for 5-LTand 6, respectively. Consecutive metamagnetic transitions in the spin ladder compound 6are due to dipolar interchain interactions. A convenient formula for susceptibility of the ferromagnetic Heisenberg chain of isotropic spins S= 1 is proposed, based on numerical DMRG calculations, and used to determine exchange constants.

Published
2018
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274. Advances in the modelling of in-situ powder diffraction data

Author

Dinnebier, Robert E., Scardi, Paolo, Müller, Melanie, Dinnebier, Robert E., Scardi, Paolo, and Müller, Melanie

Abstract

X-ray powder diffraction is a well-established technique to analyse structural and microstructural properties of materials. The possibility to record in-situ powder diffraction data allows studying changes within the structure and microstructure of a sample that occur in dependence on the applied external conditions (e.g. temperature, pressure). In the present thesis, in-situ X-ray powder diffraction was used to study structural and microstructural changes of different samples occurring at elevated temperature or upon UV illumination. Several structural phase transitions were studied using the approach of parametric Rietveld refinement. In parametric Rietveld refinement a set of powder diffraction pattern is refined simultaneously, constraining the evolution of some parameters using mathematical models, so that only the variables of the model need to be refined. In order to model and analyse the behaviour of structural parameters, Landau theory and its corresponding equations were used, owing to the fact that structural parameters (e.g. lattice strain, changes in atomic positions or occupancy) comprise an order parameter as defined in Landau theory. For description of the crystal structure of materials, several different approaches were tested, e.g. atomic coordinates, symmetry modes, rigid body rotations or rigid body symmetry modes. The dependence of preparation conditions on the properties of nanomaterials and their growth kinetics was studied using Whole Powder Pattern Modelling. This method allows modelling X-ray powder diffraction pattern using the microstructure of the sample without the use of arbitrary profile functions. The Fourier transforms of frequently observed effects as crystallite shape and size distribution or density of various defects, like dislocations and stacking faults, are utilised in order to get the resulting diffraction profile. Two different systems with industrial application, CeO2 and Cu2ZnSnS4, which were produced using a sol-gel appr

Published
2013

282. Inside Back Cover: Real-Time In Situ Powder X-ray Diffraction Monitoring of Mechanochemical Synthesis of Pharmaceutical Cocrystals (Angew. Chem. Int. Ed. 44/2013)

Author

Halasz, Ivan, primary, Puškarić, Andreas, additional, Kimber, Simon A. J., additional, Beldon, Patrick J., additional, Belenguer, Ana M., additional, Adams, Frank, additional, Honkimäki, Veijo, additional, Dinnebier, Robert E., additional, Patel, Bhavnita, additional, Jones, William, additional, Štrukil, Vjekoslav, additional, and Friščić, Tomislav, additional

Published
2013
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283. Innenrücktitelbild: Real-Time In Situ Powder X-ray Diffraction Monitoring of Mechanochemical Synthesis of Pharmaceutical Cocrystals (Angew. Chem. 44/2013)

Author

Halasz, Ivan, primary, Puškarić, Andreas, additional, Kimber, Simon A. J., additional, Beldon, Patrick J., additional, Belenguer, Ana M., additional, Adams, Frank, additional, Honkimäki, Veijo, additional, Dinnebier, Robert E., additional, Patel, Bhavnita, additional, Jones, William, additional, Štrukil, Vjekoslav, additional, and Friščić, Tomislav, additional

Published
2013
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285. Real-Time In Situ Powder X-ray Diffraction Monitoring of Mechanochemical Synthesis of Pharmaceutical Cocrystals

Author

Halasz, Ivan, primary, Puškarić, Andreas, additional, Kimber, Simon A. J., additional, Beldon, Patrick J., additional, Belenguer, Ana M., additional, Adams, Frank, additional, Honkimäki, Veijo, additional, Dinnebier, Robert E., additional, Patel, Bhavnita, additional, Jones, William, additional, Štrukil, Vjekoslav, additional, and Friščić, Tomislav, additional

Published
2013
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295. Crystal Structure and Hydrate Water Content of Synthetic Hellyerite, NiCO3·5.5H2O.

Author

Bette, Sebastian, Rincke, Christine, Dinnebier, Robert E., and Voigt, Wolfgang

Subjects
CRYSTAL structure, NICKEL carbonates, AQUEOUS solutions, X-ray powder diffraction, MONOCLINIC crystal system
Abstract

A sample of pure, artificial hellyerite was synthesized in aqueous solution at 0 °C. The recorded X-ray diffraction pattern completely agrees with the reference data given for natural hellyerite. Laboratory high resolution X-ray powder diffraction, applying global optimization methods and Rietveld refinement, was employed to solve the crystal structure. Synthetic hellyerite was determined to crystallize in the primitive monoclinic space group P2/ m (no. 10) with a = 10.769(2) Å, b = 7.295(2) Å, c = 9.343(2) Å, and β = 94.042(2)°. The crystal structure consists of edge-linked, isolated pairs of Ni2(CO3)2(H2O)8 octahedra and non-coordinating water molecules. According to structure solution and thermal analysis the molecular formula of hellyerite was corrected from NiCO3 ·6H2O to NiCO3 ·5.5H2O. The title compound was characterized by scanning electron microscopy, IR-, Raman-, and UV/Vis spectroscopy. [ABSTRACT FROM AUTHOR]

Published
2016
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296. Ni3Cl2+ x(OH)4- x·2H2O: Structural, Thermal, Spectral, and Magnetic Properties in Dependence of the Chloride Content.

Author

Bette, Sebastian, Dinnebier, Robert E., Kremer, Reinhard K., and Freyer, Daniela

Subjects
*NICKEL oxides, *HYDROXIDES, *CRYSTAL structure, *X-ray powder diffraction, *AQUEOUS solutions, *MAGNETIC susceptibility
Abstract

The previously unknown nickel chloride hydroxide phases Ni3Cl2+ x(OH)4- x ·2H2O ( x = 0.26, 0.48, 0.82) have been synthesized in concentrated aqueous NiCl2 solutions and investigated in detail. Crystal structure determination from X-ray powder diffraction data revealed triple chains of distorted, edge-linked NiO6 and NiO3(O/Cl)3 octahedra as the main building blocks. The chains exhibit a layer-like configuration and therefore great structural similarity to nickel-layered hydroxy halides (Cl, Br, I) and β-Ni(OH)2. Increasing chloride content in Ni3Cl2+ x(OH)4- x ·2H2O leads to a reduction of the space group symmetry from C2/ m (12) for x = 0.26 and 0.48 to P $\bar {1}$ (2) for x = 0.82 and to distinct shifts in their thermal, spectral, and magnetic properties. Each solid exhibits a maximum magnetic susceptibility in the range 5.9-9.7 K, which indicates antiferromagnetic ordering. Positive Curie-Weiss temperatures, θ, were found, which points to predominantly ferromagnetic spin-exchange interactions. In addition, broad maxima of the magnetic susceptibility evidence a low-dimensional magnetic character as the most prominent feature of the magnetic properties of the investigated phases. [ABSTRACT FROM AUTHOR]

Published
2016
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297. Synthesis, Structures and Properties of Cobalt Thiocyanate Coordination Compounds with 4-(hydroxymethyl)pyridine as Co-ligand.

Author

Suckert, Stefan, Werner, Julia, Näther, Christian, Germann, Luzia S., and Dinnebier, Robert E.

Subjects
COBALT compounds synthesis, COORDINATION compounds, PYRIDINE
Abstract

Reaction of Co(NCS)2 with 4-(hydroxymethyl)pyridine (hmpy) leads to the formation of six new coordination compounds with the composition [Co(NCS)2(hmpy))4] (1), [Co(NCS)2(hmpy)4] x H2O (1-H2O), [Co(NCS)2(hmpy)2(EtOH)2] (2), [Co(NCS)2(hmpy)2(H2O)2] (3), [Co(NCS)2(hmpy)2]n·4 H2O (4) and [Co(NCS)2(hmpy)2]n (5). They were characterized by single crystal and powder X-ray diffraction experiments, thermal and elemental analysis, IR and magnetic measurements. Compound 1 and 1-H2O form discrete complexes, in which the Co(II) cations are octahedrally coordinated by two terminal thiocyanato anions and four 4-(hydroxymethyl)pyridine ligands. Discrete complexes were also observed for compounds 2 and 3 where two of the hmpy ligands were substituted by solvent, either water (3) or ethanol (2). In contrast, in compounds 4 and 5, the Co(II) cations are linked into chains by bridging 4-(hydroxymethyl)pyridine ligands. The phase purity was checked with X-ray powder diffraction. Thermogravimetric measurements showed that compound 3 transforms into 5 upon heating, whereas the back transformation occurs upon resolvation. Magnetic measurements did not show any magnetic exchange via the hmpy ligand for compound 5. [ABSTRACT FROM AUTHOR]

Published
2016
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300. Harvesting of aerial humidity with natural hygroscopic salt excretions.

Author

Al-Handawi, Marieh B., Commins, Patrick, Dinnebier, Robert E., Abdellatief, Mahmoud, Liang Li, and Naumov, Panče

Subjects
*HARVESTING, *SALT crystals, *HUMIDITY, *SALT, *PLANT surfaces
Abstract

Plants and animals that thrive in arid regions utilize the diurnal changes in environmental temperature and humidity to optimize their water budget by combining water-harvesting mechanisms and morphophysiological traits. The Athel tamarisk (Tamarix aphylla) is a halophytic desert shrub that survives in arid, hypersaline conditions by excreting concentrated solutions of ions as droplets on its surface that crystallize into salt crystals and fall off the branches. Here, we describe the crystallization on the surface of the plant and explore the effects of external conditions such as diurnal changes in humidity and temperature. The salt mixtures contain at least ten common minerals, with NaCl and CaSO4·2H2O being the major products, SiO2 and CaCO3 main sand contaminants, and Li2SO4, CaSO4, KCl, K2Ca(SO4)2·H2O, CaMg(CO3)2 and AlNaSi3O8 present in smaller amounts. In natural conditions, the hanging or sitting droplets remain firmly attached to the surface, with an average adhesion force of 275 ± 3.5 µN measured for pure water. Rather than using morphological features of the surface, the droplets adhere by chemical interactions, predominantly by hydrogen bonding. Increasing ion concentration slightly increases the contact angle on the hydrophobic cuticle, thereby lowering surface wettability. Small amounts of lithium sulfate and possibly other hygroscopic salts result in strong hygroscopicity and propensity for deliquescence of the salt mixture overnight. Within a broader context, this natural mechanism for humidity harvesting that uses environmentally benign salts as moisture adsorbents could provide a bioinspired approach that complements the currently available water collection or cloud-seeding technologies. [ABSTRACT FROM AUTHOR]

Published
2023
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