Publications

A mas NMR investigation of lead phosphosilicate glasses: The nature of the highly deshielded six-coordinated silicon

29Si and 31P NMR spectra have been studied in a series of lead phosphosilicate glasses. It is found that as the P2O5 content increases, the signal due to the six-coordinated silicon at − 212 ppm grows in intensity. Based on partial charge arguments it is suggested that the six-coordinated silicon atoms are surrounded by only phosphorus as second neighbours and are highly desheilded.

123, 247, and 124 cuprate superconductors: Investigations of thermodynamic stabilities, defect structures, and intergrowths

Careful investigations employing nonresonant microwave or rf absorption, Cu2+ EPR spectra, X-ray diffraction, and electron microscopy show that orthorhombic YBa2Cu3O7−δ is thermodynamically stable and monophasic when δ is 0.0–0.2 (T c = 90 K), 0.25 (T c = 80 K), and 0.5 (T c = 45 K). The last two compositions are associated with ordered oxygen-vacancy structures; in the δ = 0.0–0.2 regime, 3b = c. Compositions in the range δ = 0.3–0.4 (T c = 60 K) do not appear to be thermodynamically stable and decompose on annealing, suggesting thereby that the so-called 60 K superconducting phase in the YBa2Cu3O7−δ system may not be genuine. 123 cuprates prepared with excess CuO often show fringes of 124 in lattice images. Both 124 and 247 cuprates prepared by the ceramic method in a flowing oxygen atmosphere frequently show intergrowths of each other or with 123. Such epitaxial relationships between 123, 124, and 247 cuprates could be of significance with respect to their superconducting properties. Both 124 and 247 cuprates undergo thermal decomposition to give 123 and CuO.

CCDC 112930: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Nanowires, nanobelts and related nanostructures of Ga2O3

By carrying out the reaction of Ga2O3 powder with carbon nanotubes around 1100 °C, nanowires, nanobelts and nanosheets of Ga2O3 have been obtained, the diameter and proportion of the nanowires depending on the flow rate of argon through the reaction zone. Reaction of Ga2O3 powder with activated carbon mainly gives rise to nanosheets and nanorods. The procedures employed in this study are attractive since they give high yields of nanowires and nanobelts. The nanowires are single crystalline with the growth direction perpendicular to the ( 1 ̄ 02) planes. The Ga2O3 nanowires exhibit good photoluminescence characteristics.

Synthesis and Isomerization of Substituted 5-Amino-1,2,3-triazoles¹

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and Isomerization of Substituted 5-Amino-1,2,3-triazoles1EUGENE LIEBER, TAI SIANG CHAO, and C. N. RAMACHANDRA RAOCite this: J. Org. Chem. 1957, 22, 6, 654–662Publication Date (Print):June 1, 1957Publication History Published online1 May 2002Published inissue 1 June 1957https://doi.org/10.1021/jo01357a018RIGHTS & PERMISSIONSArticle Views502Altmetric-Citations62LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Occurrence of maximum <i>T</i> <i>c</i> at an optimal carrier concentration in superconducting bismuth and thallium cuprates

The superconducting transition temperatures in Bi2Ca1−xLnxSr2Cu2O8+δ, TlCa1−xLnxSr2Cu2O6+δ, and Tl0.8Ca1−xLnxBa2Cu23O6+δ (Ln=Y or rare earth) vary with composition and show a maximum at a specific value of x or δ. This observation suggests that an optimal carrier concentration is required to attain maximum Tc in such cuprates which seem to be two-band systems.

COLOSSAL MAGNETORESISTANCE, CHARGE ORDERING AND OTHER NOVEL PROPERTIES OF MANGANATES AND RELATED MATERIALS

No abstract is provided for this article.

CCDC 632511: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Structure and dynamics of polar liquids: A molecular dynamics investigation of N,N-dimethyl formamide

A molecular dynamics study of liquid N,N-dimethyl formamide has been carried out. Orientational correlation functions suggest a stacked antiparallel ordering at short distances (< 5Å) and a perpendicular + configuration at intermediate distances. The proposed ordering is in agreement with the recent 13C NMR results of Konrat and Sterk and suggests a stronger association of CH3(t) with O than of CH3(c) with O. Both the translational and the rotational motions are anisotropic. The diffusion constants for rotation along the different directions are different, in agreement with the NMR results.

A Raman spectroscopic study of the plastically crystalline state of organic compounds

The depolarized and polarized components of internal Raman bands of succinonitrile, t -butyl chloride and t -butyl bromide in their plastic crystalline and liquid phases have been analyzed to obtain rotational and vibrational correlation functions. The rotational correlation times are continuous through the plastic-liquid transition and show an Arrhenius behaviour, from which activation energies for rotation have been calculated. Vibrational correlation times are nearly constant in the range of temperature investigated, except for a small change near the plastic-liquid phase transition temperature.

Coordination Polymers and Hybrid Networks of Different Dimensionalities Formed by Metal Sulfites

In our effort to explore the use of the sulfite ion to design hybrid and open-framework materials, we have been able to prepare, under hydrothermal conditions, zero-dimensional [Zn(C12H8N2)(SO3)].2H2O, I (a = 7.5737(5) A, b = 10.3969(6) A, c = 10.3986(6) A, alpha = 64.172(1) degrees , beta = 69.395(1) degrees , gamma = 79.333(1) degrees , Z = 2, and space group P), one-dimensional [Zn2(C12H8N2)(SO3)2(H2O)], II (a = 8.0247(3) A, b = 9.4962(3) A, c = 10.2740(2) A, alpha = 81.070(1) degrees , beta = 80.438(1) degrees , gamma = 75.66(5) degrees , Z = 2, and space group P), two-dimensional [Zn2(C10H8N2)(SO3)2].H2O, III (a = 16.6062(1) A, b = 4.7935(1) A, c = 19.2721(5) A, beta = 100.674(2) degrees , Z = 4, and space group C2/c), and three-dimensional [Zn4(C6H12N2)(SO3)4(H2O)4], IV (a = 11.0793(3) A, c = 8.8246(3) A, Z = 2, and space group P42nm), of which the last three are coordination polymers. A hybrid open-framework sulfite-sulfate of the composition [C2H10N2][Nd(SO3)(SO4)(H2O)]2, V (a = 9.0880(3) A, b = 6.9429(2) A, c = 13.0805(5) A, beta = 91.551(2) degrees , Z = 2, and space group P21/c), with a layered structure containing metal-oxygen-metal bonds has also been described.

Ferromagnetic resonance in Sr2+ doped rare earth orthocobaltites, Ln1−xSrxCoO3†

FMR measurements have been carried out on several members of the Ln1−x SrxCoO3 (Ln = Rare earth) system. The results show that g eff in these systems is around 1.25 independent of x as well as the rare earth ion. It is suggested that this unusual value of g eff is due to the localized intermediate-spin Co3+ ions (t 5 2g e 1 g) located at the top of the π∗ band.

Investigations of transition-metal clusters deposited on solid substrates by photoelectron spectroscopy, bremsstrahlung isochromat spectroscopy and related techniques

The 2p core-level binding energies of Cu and Ni clusters increase while the kinetic energies of the LMM Auger lines decrease with decreasing cluster size. The shifts in the core-level binding energy and the Auger kinetic energy relative to the bulk metal are largest in the case of clusters deposited on an insulating substrate such as Al2O3 and least on amorphous carbon; shifts on TiO2 are intermediate between those on Al2O3 and carbon. The increase in core-level binding energies with decreasing cluster size signifies a metal to non-metal transition. The occurrence of such a transition is borne out more vividly by BIS studies. Accordingly, BIS studies on Pd clusters deposited on amorphous carbon clearly show that electron states are progressively introduced near the Fermi level with increase in cluster size. The chemical reactivity of transition-metal clusters varies with the size. Thus, the relative proportion of the atomic oxygen species increases with decreasing size of Ag clusters.

An organically templated iron sulfate with a distorted Kagome lattice exhibiting unusual magnetic properties

A layered iron sulfate of the composition [H3N(CH2)2NH2(CH2)2NH2(CH2)2NH3][FeII3F6(SO4)2], possessing a distorted Kagome lattice, prepared hydrothermally, is found to exhibit magnetic hysteresis like a ferrimagnet besides the characteristics of a frustrated system, like those of a spin glass.

Borocarbonitrides as Metal‐Free Catalysts for the Hydrogen Evolution Reaction

Hydrogen generation by water splitting is clearly a predominant and essential strategy to tackle the problems related to renewable energy. In this context, the discovery of proper catalysts for electrochemical and photochemical water splitting assumes great importance. There is also a serious intent to eliminate platinum and other noble metal catalysts. To replace Pt by a non‐metallic catalyst with desirable characteristics is a challenge. Borocarbonitrides, (B x C y N z ) which constitutes a new class of 2D material, offer great promise as non‐metallic catalysts because of the easy tunability of bandgap, surface area, and other electronic properties with variation in composition. Recently, B x C y N z composites with excellent electrochemical and photochemical hydrogen generation activities have been found, especially noteworthy being the observation that B x C y N z with a carbon‐rich composition or its nanocomposites with MoS 2 come close to Pt in electrocatalytic properties, showing equally good photochemical activity.

Shell-model calculation of defect energies in alkali halides employing crystal-independent interionic potential parameters

Structural Variations of BiMnO_3+<i>x</i>Revealed by Electron Diffraction

Electron diffraction studies have been performed on a number of samples within the series BiMnO3+x (for the range –0.11 < x < 0.16). Samples with a large value of x (either positive or negative) crystallize as a monoclinic perovskite supercell structure not dissimilar from the stoichiometric ideal. However, the variation of oxygen composition manifests itself as disorder in either the cation or anion sub-lattices, leading to a reduction in symmetry (to C2, P21 or P2). In addition, three new structures have been identified at compositions closer to the perovskite ideal. One structure is similar to a mixed cation phase reported by Hughes et al, while another is an n = 2 Ruddlesden-Popper phase; importantly both of these phases are acentric and so could support multiferroic properties. The third is as yet not fully characterised but seems to crystallise into a different monoclinic structure than the stoichiometric ideal phase.

Novel dielectric properties of glasses prepared by quenching melts of Bi Ca Sr Cu O cuprates

Glasses, prepared from the melts of Bi2(Ca, Sr)n+1 CunO2n+4 (n=1,2 and 3) have been characterized by various techniques. These glasses exhibit relatively high dielectric constants, high electrical conductivity, a ferroelectric-like dielectric hysteresis loop and pyroelectric effect at 300K. They also show weak microwave absorption at 77K.