Anisotropic Thermal Parameters Research Articles

Lattice Dynamics in the NASICON NaZr2(PO4)3 Solid Electrolyte from Temperature-Dependent Neutron Diffraction, NMR, and Ab Initio Computational Studies

Natrium super ionic conductor (NASICON) compounds form a rich and highly chemically tunable family of crystalline materials that are of widespread interest because they include exemplars with high ionic conductivity, low thermal expansion, and redox tunability. This makes them suitable candidates for applications ranging from solid-state batteries to nuclear waste storage materials. The key to an understanding of these properties, including the origins of effective cation transport and low, anisotropic (and sometimes negative) thermal expansion, lies in the lattice dynamics associated with specific details of the crystal structure. Here we closely examine the prototypical NASICON compound, NaZr2(PO4)3, and obtain detailed insights into such behavior via variable-temperature neutron diffraction and 23Na and 31P solid-state NMR studies, coupled with comprehensive density functional theory-based calculations of NMR parameters. Temperature-dependent NMR studies yield some surprising trends in the chemical shifts and the quadrupolar coupling constants that are not captured by computation unless the underlying vibrational modes of the crystal are explicitly taken into account. Furthermore, the trajectories of the sodium, zirconium, and oxygen atoms in our dynamical simulations show good qualitative agreement with the anisotropic thermal parameters obtained at higher temperatures by neutron diffraction. The work presented here widens the utility of NMR crystallography to include thermal effects as a unique probe of interesting lattice dynamics in functional materials.

Desolvation–Solvation-Induced Reversible On–Off Switching of Two Memory Channels in a Cobalt(II) Coordination Polymer: Overlay of Spin Crossover and Structural Phase Transition

Desolvation–Solvation-Induced Reversible On–Off Switching of Two Memory Channels in a Cobalt(II) Coordination Polymer: Overlay of Spin Crossover and Structural Phase Transition

Thermally Induced Reversible Metal-to-Metal Charge Transfer in Mixed-Valence {Fe III 4 Fe II 4 } Cubes

Thermally Induced Reversible Metal-to-Metal Charge Transfer in Mixed-Valence {Fe ^III ₄ Fe ^II ₄ } Cubes

Guest-Mediated Hierarchical Self-Assembly of Dissymmetric Organic Cages to Form Supramolecular Ferroelectrics

Guest-Mediated Hierarchical Self-Assembly of Dissymmetric Organic Cages to Form Supramolecular Ferroelectrics

Synthesis, structure, optical and thermal analysis of the new compound of the new compound organo-metallic (C5H6N)2TeCl6

A new organic-inorganic phase compound (C5H6N)2TeCl6, was synthesized and its structure was determined at room temperature in the monoclinic system (C2/m space group) with the following lattice parameters: a = 12.9000(18) Å, b = 8.4777(12)Å, c = 8.0127(11)Å and β = 96.860(2)°. The final refinement cycle of all isotropic and anisotropic thermal parameters led to R = 0.026 and wR = 0.03. The anion and cation chains are linked by N-H…Cl hydrogen bonds.The infrared spectra were recorded in the 4000–400 cm−1 frequency region. The Raman spectra were recorded in the external region of the anionic sublattice vibration 50–1500 cm−1. The optical band gap was calculated from the UV-Vis absorbance spectra using classical Tauc relation which was found to be 2.48 eV. Several thermal analysis techniques such as thermogravimetric analysis, differential scanning calorimetric analysis and evolved gas analysis were used. We observe that the decomposition of (C5H6N)2TeCl6 occurs between 473 and 573 K with the formation of pyridine, HCl, Cl2 and N2 as volatiles.

Partial Order–Disorder Transformation of Interpenetrated Porous Coordination Polymers

Controlling interpenetration and flexibility behaviors is intriguing and fundamental for porous coordination polymers. We report exceptional interpenetration behaviors involving controllable partia...

Efficient Photogeneration of Hydrogen Boosted by Long-Lived Dye-Modified Ir(III) Photosensitizers and Polyoxometalate Catalyst

Efficient Photogeneration of Hydrogen Boosted by Long-Lived Dye-Modified Ir(III) Photosensitizers and Polyoxometalate Catalyst

Secondary Metal Coordination Using a Tetranuclear Complex as Ligand Leading to Hexanuclear Complexes with Enhanced Thermal Barriers for Electron Transfer

Postsynthesis of the paramagnetic square-shaped complex {[(Tp*Me)Fe(μ-CN)2(CN)][Co(dmbpy)2]}2(BPh4)2·6MeCN·H2O [1, Tp*Me = tris(3,4,5-trimethylpyrazole)-borate; dmbpy = 4,4′-dimethyl-2,2′-bipyridin...

Synthesis, structure, optical and thermal analysis of the new compound (C3N6H7)2Te(OH)6.2Cl

A new organic-inorganic phase [(C3N6H7)2Te(OH)6.2Cl]has been synthesized by a wet method and characterized by X-ray single crystal diffraction, infrared and Raman spectroscopy and thermal analysis. This compound is found to crystallize in a triclinic space group P1¯. The final refinement cycle of all isotropic and anisotropic thermal parameters led to R = 0.026 and wR = 0.03. The atomic arrangement can be described as an alternation of organic and inorganic layers along the a-axis. The crystal packing is governed by the N–H⋯Cl, O–H⋯Cl and non-classical N–H⋯N hydrogen bonding interactions, the latter plays a key role in the stabilization of the crystal structure. Thermal decomposition of the title compounds involves three stages; dehydration, formation of different tellurium oxides and the decomposition of the organic part to form a polymer product called "melon". The last stage entails the complete removal of the organic part and formation of TeO2.

Structural disorder and magnetic correlations driven by oxygen doping in Nd2NiO4+δ ( δ∼0.11 )

We investigated the influence of oxygen over-stoichiometry on apical oxygen disorder and magnetic correlations in Nd2NiO4+d (d~0.11) in the temperature range of 2-300 K by means of synchrotron x-ray powder diffraction, neutron single crystal and powder diffraction studies, combined with macroscopic magnetic measurements. In the investigated temperature range, the compound crystalizes in a tetragonal commensurate structure with the P42/ncm space group with excess oxygen atoms occupy the 4b (3/4 1/4 1/4) interstitial sites, coordinated by four apical oxygen atoms. Large and anisotropic thermal displacement parameters are found for equatorial and apical oxygen atoms, which are strongly reduced on an absolute scale compared to the Nd2NiO4.23 phase. Maximum Entropy analysis of the neutron single crystal diffraction data uncovered anharmonic contributions to the displacement parameters of the apical oxygen atoms, toward the nearest vacant 4b interstitial site, related to the phonon assisted oxygen diffusion mechanism. Macroscopic magnetization measurements and neutron powder diffraction studies reveal long-range antiferromagnetic ordering of the Ni-sublattice at TN ~ 53 K with a weak ferromagnetic component along the c-axis, while the long-range magnetic ordering of the Nd-sublattice occurs below 10 K. Temperature dependent neutron diffraction patterns show the appearance of a commensurate magnetic order at TN with the propagation vector k = (100) and the emergence of an additional incommensurate phase below 30 K, while both phases coexist at 2 K. The commensurate magnetic structure is best described by the P42/nc`m` Shubnikov space group. Refined magnetic moments of the Ni and Nd-sites at 2 K are 1.144(76) muB and 1.632(52) muB respectively. A possible origin of the incommensurate phase is discussed and a tentative magnetic phase diagram is proposed.

Structure and properties of nature clathrate and its application in energy and enviromental science

Clathrate hydrates are energy and environmental related materials for energy storage and extraction, as well as for waste gas sequestration. The three general structures of natural clathrates, structure I, structure Ⅱ and structure H are reviewed in the aspects of stability, cage size, and preferred guest molecule encapsulation. Neutron scattering technique has its unique advantage of clathrate hydrates characterization, such as large bulk property determination, penetration of high pressure vessel and the clathrate sample inside, sensitive to light elements (clathrate hydrates mainly containing C, H, and O atoms). Neutron diffraction and inelastic neutron scattering of clathrate hydrates are covered on the abilities of H/D atoms positions and anisotropic thermal parameters, pressure-temperature-dependent guest molecule occupancy, the disordered distributions of guest molecules and the nuclear density distributions, the thermodynamic and kinetic process of formation and decomposition, the translational and rotational vibration models of guest molecules and their quantum state transitions. Using CO<sub>2</sub> to gently replace CH<sub>4</sub> in methane hydrate is one of the most attractive exploiting schemes for its benefits to both geologic hazard consideration and cost efficiency (energy extraction and CO<sub>2</sub> sequestration).

The Fluorite-Like Phase Nd5Mo3O16±δ in the MoO3-Nd2O3 System: Synthesis, Crystal Structure, and Conducting Properties.

This paper describes a study of the system MoO3-Nd2O3 using a combination of X-ray powder diffraction (XRD), neutron powder diffraction (NPD), thermogravimetric analysis (TGA), and ac impedance spectroscopy (IS). A phase-pure material is observed at a composition of 45.5 mol % Nd2O3, which corresponds to an ideal stoichiometry of Nd5Mo3O16.5. XRD and NPD show that the crystal structure is a superstructure of the fluorite arrangement, with long-range ordering of the two cation species leading to a doubled unit cell parameter. The sample is found to be significantly oxygen deficient, i.e. Nd5Mo3O15.63(4), when it is prepared by a solid-state reaction at 1473 K in air. TGA measurements indicate that the sample loses only minimal mass on heating to 1273 K in O2. IS studies of the mean conductivity under different atmospheres show that the sample is a mixed conductor between ambient temperature and 873 K, with a dominant electronic component at higher temperatures, as demonstrated by measurements under inert atmosphere. NPD measurements indicate that the anion vacancies are preferentially located on the O2 sites, while studies of the temperature dependence performed under an O2 atmosphere to 1273 K show significantly anisotropic thermal parameters of the anions. Together with analysis of the total neutron scattering data, this supports a model of oxygen ions hopping between O2 positions, with a vacancy, rather than interstitial, mechanism for the anion diffusion.

Synthesis, Crystal Structure, and Transport Properties of the Hexagonal Mo9 Cluster Compound Ag3RbMo9Se11.

Mo-based cluster compounds are promising candidates for thermoelectric applications at high temperatures due to their very low lattice thermal conductivity values. Here, we report on a detailed investigation of the crystal structure and transport properties measured in a wide range of temperatures (2-800 K) of polycrystalline Ag3RbMo9Se11. Single-crystal X-ray diffraction shows that this compound crystallizes in the hexagonal space group P63/m. The crystal structure is formed by stacked Mo9Se11 units leaving channels that are randomly filled by Rb+ cations, while Ag+ cations are located between the Mo9Se11 units. The high disorder in the unit cell induced by these atoms and their large anisotropic thermal displacement parameters are two key characteristics that lead to very low lattice thermal conductivity as low as 0.6 W m-1 K-1 at 800 K. The combination of semiconducting-like electrical properties and low ability to transport heat leads to a maximum dimensionless thermoelectric figure of merit ZT of 0.4 at 800 K.

Crystal Structure of 4,4′-Bi(3-(1-methylethoxy)-3-cyclobutene-1,2-dione)

Bisquaric acid, a hydrolysed form of 4,4¢-bi(3-(1methylethoxy)-3-cyclobutene-1,2-dione) (title compound, Fig. 1), reported by Liebeskind et al.1 possesses unique characteristics in the single-crystal phase, such as a dielectric response2 and an increase in the p-resonance,3 due to proton migration via quasi-one-dimensional hydrogen bonding. These characteristics originate from the concerted dynamics of the p-electrons and proton involved in strong hydrogen bonding, which has been confirmed by crystal structure, 13C-NMR, and DFT analyses. Most of the discussion emphasises the effect of hydrogen bonding. Further, the property originating from a bisquaric framework is not well considered. Accordingly, we analysed the single-crystal structure of the title compound in which the hydrogen bonding is quenched so as to investigate the p-electron system in the molecular framework. The title compound and its single crystal were prepared by Liebeskind’s method.1 The single crystal was mounted on a glass capillary, transferred to a Bruker AXS SMART APEX diffractometer equipped with a CCD area detector and Mo Ka (l = 0.71073 A) radiation, and centred in the beam at room temperature (293 K). The structure was solved and refined with SHELXS-97 and SHELXL-2014/7 (ref. 4), respectively, by the direct method before being expanded by Fourier techniques. A least-squares refinement was first carried out with all nonhydrogen atoms refined isotropically, with a subsequent assignment of the anisotropic thermal parameters to these atoms to achieve convergence. Hydrogen atoms were located by difference Fourier mapping, and all parameters were refined. All isotropic displacements of the hydrogen atoms were greater than the equivalent isotropic displacements of their connecting atoms. Crystal data are given in Table 1, as well as an ORTEP view is illustrated by ORTEP-3 (ref. 5). The atom numbering scheme is shown in Fig. 2. PLATON software6 suggested the presence of very weak intramolecular (C5–H5·O2) and intermolecular (C5– H5·O1i) hydrogen bonds. However, these are non-classical hydrogen bonds, and hence are insignificant for conjugated p-electron systems due to the low probability of proton migration. Table 2 summarises the lengths of the weak hydrogen bonds and C–C bonds of four membered ring and linker bond. The length of the C1–C4 bond is similar to that of the ethylene carbon–carbon double bond (1.33 A),7 while the cyclic linker C1–C1a and the adjacent C1–C2 bond lengths are similar to the sp2–sp2 bond length (1.47 A).7 On the other hand, the C2–C3 and C3–C4 bonds are shorter than the carbon–carbon Crystal Structure of 4,4¢-Bi(3-(1-methylethoxy)-3-cyclobutene-1,2-dione)

Host perturbation in a β-hydroquinone clathrate studied by combined X-ray/neutron charge-density analysis: implications for molecular inclusion in supramolecular entities.

X-ray/neutron (X/N) diffraction data measured at very low temperature (15 K) in conjunction with ab initio theoretical calculations were used to model the crystal charge density (CD) of the host-guest complex of hydroquinone (HQ) and acetonitrile. Due to pseudosymmetry, information about the ordering of the acetonitrile molecules within the HQ cavities is present only in almost extinct, very weak diffraction data, which cannot be measured with sufficient accuracy even by using the brightest X-ray and neutron sources available, and the CD model of the guest molecule was ultimately based on theoretical calculations. On the other hand, the CD of the HQ host structure is well determined by the experimental data. The neutron diffraction data provide hydrogen anisotropic thermal parameters and positions, which are important to obtain a reliable CD for this light-atom-only crystal. Atomic displacement parameters obtained independently from the X-ray and neutron diffraction data show excellent agreement with a |ΔU| value of 0.00058 Å(2) indicating outstanding data quality. The CD and especially the derived electrostatic properties clearly reveal increased polarization of the HQ molecules in the host-guest complex compared with the HQ molecules in the empty HQ apohost crystal structure. It was found that the origin of the increased polarization is inclusion of the acetonitrile molecule, whereas the change in geometry of the HQ host structure following inclusion of the guest has very little effect on the electrostatic potential. The fact that guest inclusion has a profound effect on the electrostatic potential suggests that nonpolarizable force fields may be unsuitable for molecular dynamics simulations of host-guest interaction (e.g., in protein-drug complexes), at least for polar molecules.

Dependence of the Li-Ion Conductivity and Activation Energies on the Crystal Structure and Ionic Radii in Li6MLa2Ta2O12

Inspired by the promising ionic conductivities of the lithium conducting garnets, we present a comparative study on the influence of the ionic radius of M(2+) on the 8-coordinate site and the crystal structure on the ionic transport in the solid solution Li6MLa2Ta2O12. Neutron diffraction and synchrotron diffraction in combination with AC impedance measurements are employed to understand the systematic substitution with different-sized alkaline earth cations M(2+). As may be expected, the unit-cell parameters increase linearly with increasing ionic radius from Ca(2+) over Sr(2+) to Ba(2+), accompanied by an increase in the polyhedral volumes of the dodecahedral, and tetrahedral positions and the ionic conductivities. While the TaO6 octahedral volume remain constant, the anisotropic thermal parameters of the coordinating oxygen anions suggest a high degree of rotational freedom with increasing unit-cell size. These structural parameters lead to lower activation energies because of broader Li conduction pathways and a higher flexibility in the crystal lattice, ultimately controlling the ionic conductivities in this class of materials.

Single-crystal Structure of Cd2+-exchanged Zeolite Y (FAU, Si/Al = 1.56), |Cd27.5(Cd8O4)2.5|[Si117Al75O384]-FAU

Zeolite framework contains channels and windows and interconnected voids which are occupied by the cations and water molecules. The cations are quite mobile and may usually be exchanged by other cations. Ion exchange is the most important method for the modification of the physical and chemical properties of zeolites for use as catalysts, sorbents, and molecular sieves. The results of ion exchange into zeolites from aqueous solution are usually not simple. Often only a fraction of the original cations can be replaced, and attempts to overcome this may reveal a relatively sharp upper limit to exchange. When acetate salt of metal cations dissolves in water for exchange solution, metal hydroxide ions occurred. It can be exchanged for Na ions into zeolite framework, leading to over exchange. The catalytic activity of Cd-exchanged zeolite Y for the formation of acetonitrile was studied for comparison with activated alumina (Al2O3) and also examined for the formation of acetonitrile from ethane and ammonia. Its catalytic activity had much higher than that of Al2O3. It was found to be essentially inactive for the formation of acetonitrile from ethylamine. When zeolite Y (Si/Al = 1.69) was ion exchanged in aqueous stream 0.05 M in Cd (0.025 M Cd(NO3)2 and 0.025 M Cd(C2H3O2)2) for 5 days and dehydrated at 723 K and 2 × 10 Torr for 2 days, the resulting composition, |Cd27.5(Cd8O4)2| [Si121Al71O384]-FAU, indicated that eight molecules of Cd(OH)2 had been imbibed per unit cell. With eight nonframework oxides, two Cd8O4 clusters had formed per unit cell. It was stated that the ability of Cd ions to hydrolyze at pH 7 facilitated this process, as did the ability of the sodalite unit to host and stabilize Cd4(OH)4 clusters. This study was done to investigate the behavior of Cd in Cd-exchanged zeolite Y (Si/Al = 1.56) prepared at high ion-exchange temperature (353 K), with the expectation of forming more cadmium oxide cluster, Cd8O4. Synchrotron X-ray diffraction data were collected at 100 (1) K using an ADSC Quantum 210 detector at Beamline 6B MXI at the Pohang Light Source. Crystal evaluation and data collection were done using λ = 0.90000 A radiation with a detector-to-crystal distance of 60 mm. Preliminary cell constants and an orientation matrix were determined from 72 sets of frames collected at scan intervals of 5 with an exposure time of 1 second per frame. The basic scale file was prepared using the program HKL 2000. The reflections were successfully indexed by the automated indexing routine of the DENZO program. The 87,989 reflections were harvested by collecting 144 sets of frames with 5 scans and an exposure time of 1 second per frame. These highly redundant data sets were corrected for Lorentz and polarization effects, and (negligible) corrections for crystal decay were also applied. The cubic space group was determined by the program XPREP. The summary of the experimental and crystallographic data is presented in Table 1. Full-matrix least-squares refinement (SHELXL97) was done on Fo using all data. Refinement was initiated with the atomic parameters of the framework atoms [(Si,Al), O(1), O(2), O(3), and O(4)] in dehydrated |Tl75| [Si117Al75O384]-FAU. Initial refinement used anisotropic thermal parameters and Fd3m

Intermolecular Interactions and Electrostatic Properties of the β-Hydroquinone Apohost: Implications for Supramolecular Chemistry

The crystal structure of the β-polymorph of hydroquinone (β-HQ), the apohost of a large family of clathrates, is reported with a specific focus on intermolecular interactions and the electrostatic nature of its cavity. Hirshfeld surface analysis reveals subtle close contacts between two interconnecting HQ networks, and the local packing and related close contacts were examined by breakdown of the fingerprint plot. An experimental multipole model containing anisotropic thermal parameters for hydrogen atoms has been successfully refined against 15(2) K single microcrystal synchrotron X-ray diffraction data. The experimental electron density model has been compared with a theoretical electron density calculated with the molecule embedded in its own crystal field. Hirshfeld charges, interaction energies and the electrostatic potential calculated for both models are qualitatively in good agreement, but small differences in the electrostatic potential persist due to charge transfer from all hydrogen atoms to the oxygen atoms in the theoretical model. The electrostatic potential in the center of the cavity is positive, very shallow and highly symmetric, suggesting that the inclusion of polar molecules in the void will involve a balance between opposing effects. The electric field is by symmetry zero in the center of the cavity, increasing to a value of 0.0185 e/Å(2) (0.27 V/Å) 1 Å along the 3-fold axis and 0.0105 e/Å(2) (0.15 V/Å) 1 Å along the perpendicular direction. While these values are substantial in a macroscopic context, they are quite small for a molecular cavity and are not expected to strongly polarize a guest molecule.

Low Temperature X-Ray Crystallographic Structure of the Antiplasmodial Compound 5-N-Hydroxyethanequindoline Hydrochloride 0.5CH3OH

The structure of 5-N-hydroxyethanequindoline hydrochloride methanolate, C17H15ON2 Cl·½CH3OH, M r = 314.78, has been determined from X-ray diffraction data. The crystals are monoclinic, space group C2/c, with Z = 8 molecules per unit cell and a = 18.179(11), b = 7.317(5), c = 24.125(15) A, β = 110.155(10)°, V c = 3012(3) A3, crystal density D c = 1.388 Mg m−3. The structure was solved by direct methods, and the asymmetric unit comprises the 5-N-hydroxyethanequindoline hydrochloride and ½CH3OH moiety. The methanol is unusually disordered over a twofold axis with the C atom slightly removed from the twofold axis. Restraints were applied to the bond lengths of the two components of the disordered CH3OH, and to the anisotropic thermal displacement parameters of the disordered CH3OH carbon atom. The heterocyclic quindoline ring system and the first C atom of the hydroxyethane side chain are planar within 0.02 A, with the terminal C–OH atoms of the side chain significantly out of the plane. The crystal structure is maintained via three hydrogen bonds all involving the chlorine atom an oxygen in the hydroxyethane side chain, a nitrogen in the quindoline moiety and the methanol oxygen. The novel cryptolepine analogue, 5-N-hydroxyethanequindoline was synthesised as part of an ongoing exploration of cryptolepine analogues as lead compounds towards antimalarial and anticancer agents. In previous work it has been shown that halogen ring substituents enhance the antimalarial properties of cryptolepine and improve its selectivity but the effects of modification of the 5-N substituent on antiplasmodial activity has not so far been investigated. Although, the antiplasmodial activity of this analogue was found to be less than that of cryptolepine, the X-ray structure of this compound will help to determine whether or not 5-N-hydroxyethanequindoline is able to intercalate into DNA and facilitate the design of new cryptolepine analogues with DNA binding properties appropriate for antimalarial (with no DNA intercalation) or anticancer (sequence-specific binding) applications.

Structural Study of Trehalose Dihydrate by Neutron and X-ray Diffraction Experiments

The structure of α,α-trehalose dihydrate was studied by neutron and X-ray diffraction experiments to understand the relation between its superior biological protective function and the role of the hydrogen bond connecting the trehalose molecules. By direct observation of hydrogen using the neutron diffraction method, the nuclear positions and anisotropic thermal parameters of hydrogen atoms are determined accurately. The nuclear positions show clear discrepancies from the centers of the electron cloud of hydrogen determined from the X-ray data. The result is interpreted in terms of a local electric dipole moment in the hydrogen atoms. The magnitude of the dipole moment is markedly large for the hydrogen atoms participating in the hydrogen bond. The detailed electron density distribution has been determined by using X-ray data obtained at 150 K. It clearly shows the electron cloud of hydrogen spreading over the chain of hydrogen bonds. It was found that there is a part where the electron density is very lo...