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  • Inorganic Chemistry  (14)
  • Atomic, Molecular and Optical Physics  (5)
  • Surface physics, nanoscale physics, low-dimensional systems
  • 42.75
  • 1990-1994  (19)
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  • 1
    Electronic Resource
    Electronic Resource
    Papain in aqueous solution and the role of Asp-158 in the mechanism: An Ab InitioSCF + DRF + BEM study (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 40 (1991), S. 49-59 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of the solvent on the stability of the zwitterion in the active site of papain is investigated with numerical methods. The solvent is represented by a homogeneous dielectric continuum surrounding a cavity, defined by a fragment of the protein enclosed by a surface obtained following Connolly's method. The discretisized boundary surface is used to solve the Poisson equation in its integral form by means of a numerical approximation based on the boundary element method (BEM), resulting in a set of surface polarization charges. The solvent effect on the proton transfer in papain is studied on the basis of MO-SCF-direct reaction field (DRF) calculations of the energy and charge distribution of the fragment in the field of the surface charges. The role of Asp-158 in the proton transfer in the active site of papain is reevaluated in the presence of the solvent. It is concluded that the effect of the negative charge of Asp-158 is nearly completely screened by the solvent.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560400710
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  • 2
    Electronic Resource
    Electronic Resource
    Computation of scanning tunneling microscope images (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 40 (1991), S. 687-702 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article describes the computation of the tunnel current in a scanning tunneling microscope (STM). The calculation accounts for the three-dimensional scattering taking place simultaneously in the first atomic layers of the sample and in the apex of the probing tip. The model is built with the following ingredients: (a) the tip is represented by a cluster of atoms attached to an otherwise planar, free-electron metal surface, and (b) the analyzed sample is a planar free-electron metal with a local potential corrugation induced by an isolated molecule or adatom. The potential barrier includes the strong bending effect due to the image-charge formation occurring as the tunneling electron crosses the gap between the tip and the sample. The specific theoretical approach designed to solve this scattering problem exploits the fast Fourier transform algorithm to construct a transfer matrix in a mixed real- and momentum-spaces representation. The total current is obtained by summing the contributions of all scattered waves traveling in the barrier between the tip and the sample, and it is studied in this article for various positions of the tip relative to the adsorbed atomic cluster. The theory is used here to simulate the scan of a model-aluminum atom on a free-electron metal substrate using electrons focused by a single-atom tungsten tip.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560400860
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  • 3
    Electronic Resource
    Electronic Resource
    Success and pitfalls of the dielectric continuum model in quantum chemical calculations (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 48 (1993), S. 451-466 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recently we presented an extension of the direct reaction field (DRF) method, in which a quantum system and a set of point charges and interacting polarizabilities are embedded in a continuum that is characterized by a dielectric constant ∊ and a finite ionic strength. The reaction field of the continuum is found by solving the (linearized) Poisson-Boltzmann equation by a boundary element method for the complete charge distribution in a cavity of arbitrary size and form. Like many other authors, we found that the results depend critically on the choice of the size of the cavity, in the sense that the continuum contribution to the solvation energy decreases rapidly with the relative cavity size. The literature gives no clues for the definition of the cavity size beyond “physical intuition” or implicit fitting to experimental or otherwise desired results. From theoretical considerations, a number of limitations on the position of the boundary are derived. With a boundary defined within these limitations, the experimental hydration energies cannot be reproduced, mainly because of the neglected specific interactions. In addition, we found that the description of the solute's electronic states also depends on the solvation model. We suggest that one or more explicit solvent layers are needed to obtain reliable solvation and excitation energies. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560480844
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  • 4
    Electronic Resource
    Electronic Resource
    Ein Oxotellurat (VI) neuen Typs: Rb6[TeO5] [TeO4]Professor Dirk Reinen zum 60. Geburtstage am 5. Mai 1990 gewidmet (1990)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 584 (1990), S. 105-113 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A New Type of Oxotellurates (VI): Rb6[TeO5] [TeO4]For the first time single crystals of Rb6Te2O9 was obtained by annealing intimate mixtures of the binary oxides (closed Ag-cylinder in supremax-glass ampoule, 680°C, 45 d). The structure elucidation (four-circle diffractometer, AgKα, 2083 I0(hkl); R = 9.5%, Rw = 6.6%) confirms the space group C2/c with a = 1207.5(7), b = 1266.3(5), c = 1105.3(6) pm, β = 123.1(1)0, Z = 4 (Guinier-Simon photographs).Characteristic for this structure are „isolated“ trigonal bipyramidal groups of [TeO5] and „isolated“ tetrahedral groups of [TeO4], so we prefere to name the new compound Rb6[TeO5][TeO4]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, the latter derived from Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.
    Notes: Neu dargestellt wurde erstmals Rb6Te2O9 durch Erhitzen inniger Gemenge der binären Oxide in Form farbloser, unregelmäßiger Einkristalle (geschlossene Ag-Bömbchen in Supremaxampullen, 680°C, 45 d).Die Strukturaufklärung (Vierkreisdiffraktometerdaten; AgKα; 2083 I0(hkl); R = 9,5%, Rw = 6.6%) belegt die Raumgruppe C2/c. Aus Guinier-Simon-Aufnahmen folgt a = 1207,5(7), b = 1266,3(5), c = 1105,3(6) pm, β = 123,1(1)0, Z = 4.Strukturcharakteristisch sind „isolierte“ trigonal-bipyramidale Gruppen [TeO5] und „isolierte“ tetraedrische Gruppen [TeO4], was die Bezeichnung Rb6[TeO5][TeO4] richtiger erscheinen läßt. Der Madelunganteil der Gitterenergie, MAPLE, sowie Effektive Koordinationszahlen, ECoN, diese über Mittlere Fiktive Ionenradien, MEFIR, werden berechnet und diskutiert.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19905840108
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  • 5
    Electronic Resource
    Electronic Resource
    Das erste quinquinäre Oxotellurat(VI): K3Na2LiTeO6 (1990)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 586 (1990), S. 125-135 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The First Quinquinary Oxotellurate (VI): K3Na2LiTeO6Colourless single crystals of K3Na2LiTeO6 are formed by reaction of the binary oxides (closed Ag-cylinder in supremaxglass ampoule; K2O:Na2O:Li2O:TeO3 = 3:2:1:2; 720°C; 40 d). The structure elucidation (four-circle diffractometer, MoKα, 3286 symmetry independent I0(hkl); R = 1.9%) confirms the space group Cc with a = 928.3(1), b = 1187.4(2), c = 678.7(1) pm, β = 93.8(1)°, Z = 4 (Guinier-deWolff-data).Essential part of the structure are chains ∞1{LiTeO6} which are connected to sheets ∞2{Na2LiTeO6}by sodium.The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, the latter derived from Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.
    Notes: Neu dargestellt wurde aus den binären Oxiden in Form farbloser, kugeliger Einkristalle K3Na2LiTeO6 (geschlossene Ag-Bömbchen in Supremaxampullen; K2O:Na2O:Li2O:TeO3 = 3:2:1:2; 720°C; 40 d).Die Strukturaufklärung (Vierkreisdiffraktometerdaten; MoKα, 3286 I0(hkl), alle verwendet; R = 1,9%), belegt die Raumgruppe Cc. Aus Guinier-deWolff-Daten folgt a = 928,3(1), b = 1187,4(2), c = 678,7(1) pm, β = 93,8(1)°, Z = 4.Charakteristisch für die Struktur sind aus [TeO6]-Oktaeder und tetraedrischen [LiO4]-Gruppen gebildete Ketten ∞1{LiTeO6}, die über Na+zu Schichten ∞2{Na2LiTeO6} verknüpft sind.Der Madelunganteil der Gitterenergie, MAPLE, sowie Effektive Koordinationszahlen, ECoN, diese über Mittlere Fiktive Ionenradien, MEFIR, werden berechnet und diskutiert.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19905860117
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  • 6
    Electronic Resource
    Electronic Resource
    Neue Alkalimetallorthonitrate und ihre schwingungsspektroskopische Charakterisierung (1992)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 608 (1992), S. 49-55 
    Details
    ISSN: 0044-2313
    Keywords: Alkali metal orthonitrates ; preparation ; vibrational spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: New Alkali Metal Orthonitrates nad their Characterization by Vibrational SpectroscopyFor the first time the alkali metal orthonitrates Rb3NO4, Cs3NO4, AA′2NO4 (A,A′=Na, K, Rb), A3A′3(NO4)2 (A=K, Rb, Cs; A′=Na, K, Rb except Cs3Na3(NO4)2 and AA′5(NO4)2 (A,A′=Na, K) have been prepared by solid state reactions of alkali metal oxides with alkali metal nitrates. All new compounds were proved to contain NO43--groups by vibrational spectroscopy. The wavenumbers of the fundamental vibrations are strongly depending on the radius of the cations in an unexpected amount.
    Notes: Erstmals wurden die Alkalimetallorthonitrate Rb3NO4, Cs3NO4, AA′2NO4 (A,A′ =Na, K, Rb), A3A′3(NO4)2 (A=K, Cs; A′=Na, K, Rb außer Cs3Na3(NO4)2) und AA′5(NO4)2) (A,A′=Na, K) durch Festkörperreaktionen zwischen Alkalimetalloxiden und den entsprechenden Nitraten erhalten. Ihre Natur als Orthonitrate wurde schwingungsspektroskopisch belegt. Die Bandenlagen der inneren Schwingungen zeigen eine ungewöhnlich starke Abhängigkeit von der Größe der Kationen.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19926080208
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  • 7
    Electronic Resource
    Electronic Resource
    Einkristallzüchtung und Strukturanalyse von Trikaliumorthonitrat (1992)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 608 (1992), S. 56-59 
    Details
    ISSN: 0044-2313
    Keywords: Tripotassiumorthonitrate ; preparation ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Crystal Growth and X-ray Structure Determination of the TripotassiumorthonitrateThe title compound has been characterized by single crystal x-ray diffraction: 1126 diffractometer data, space group Pnma, a=10.921(1), b=7.952(1), c=5.667(1) Å, Z=4, Rw =0.024. The distance N—O in the tetrahedron oxoanion (1.398 Å) is only little, but significantly larger than in Na3NO4. More significant are the shifts of the absorption frequencies in the vibrational spectra to lower wave numbers (e.g. 24 cm-1 for the symmetric stretching mode). The anions are arranged similar to a cubic closest packing with potassium placed on all tetrahedral and octahedral sites.
    Notes: Die Kristallstruktur der Titelverbindung wurde auf der Basis von Vierkreisdiffraktometerdaten (1126 unabhängige Strukturfaktoren) gelöst und verfeinert: Raumgruppe Pnma; a = 10,921(1); b = 7,952(1); c= 5,667(1) Å Z = 4; Rw = 0,024. Der Bindungsabstand N—O im tetraedrischen Oxanion ist mit d=1,398 Å geringfügig, jedoch signifikant vergrößert gegenüber dem in Na3NO4. Deutlicher fällt eine wohl damit in Zusammenhang stehende Verschiebung der symmetrischen Streckschwingung um 24 cm-1 zu kleineren Wellenzahlen aus. Die Anionen sind im sind im Sinne einer kubisch dichtesten Anordnung gepackt, Kalium besetzt alle Tetraeder- und Oktaederlücken.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19926080209
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  • 8
    Electronic Resource
    Electronic Resource
    Zur Kenntnis des Calciumbromats und - iodats, Kristallstruktur, röntgenographische, IR- und Raman-spektroskopische und thermoanalytische Untersuchungen (1992)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 608 (1992), S. 135-144 
    Details
    ISSN: 0044-2313
    Keywords: Calcium bromate, iodate; ; X-ray ; IR ; Raman ; thermal analyses ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On Calcium Bromated and Iodates - Crystal Structure, X-Ray, IR and Raman Spectroscopical and Thermoanalytical InvestigationsThe phase relationships (and both decomposition and disproportionation)of bromates and iodates of alkaline earth metals are studied by means of thermal analyses (DTA, DSC, TG) and (high-temperature) X-Ray, IR-, and (high-temperature) Raman spectroscopic measurements. The following compounds have been established: Ca(IO3)2 · 6 H2O oF216, the isotypic Ca(BrO3)2 · H2O and Ca(IO3)2 · H2O mP48, Ca(IO3)2 I (Lautarit) mP36, Ca(IO3)2 II and Ca(BrO3)2. The Crystal structure of Ca(IO3)2 · H2O (brüggenite) (space group P21/c, Z = 4) has been determined by single crystal X-ray diffraction (MoKα). The final R value for 3888 reflections with Io 〉 3σ1 is 0.0487. The structures of bromates and iodates of alkaline earth metals known so far are discussed with respect to the energetic (mode frequencies) and geometric (bond lengths) distortion of the XO3-ions as well as the strengths of H-bonds present in the respective hydrates.
    Notes: Ca(BrO3)2 und Ca(IO)3 sowie deren Hydrate wurden mit Hilfe thermoanalytischer, röntgenographischer und IR- sowie Raman- spektroskopischer Methoden untersucht. Charakterisiert wurden: Ca(IO3)2 · 6 H2O oF216, die isotypen Monohydrate mP48 Ca(BrO3)2 νH2O und Ca(IO3)2 I (Lautarit) mP36, Ca(IO3)2 II und Ca(BrO3)2. Die Kristallstruktur von Ca(IO3)2 νH2O (Brüggenit) (Raumgruppe P21/c, Z = 4) wurde mit Hilfe von Röntgeneinkristalldaten (MoKα) bestimmt (R = 4,87%, 3888 Reflexe mit Io 〉 3σ1). Die Strukturen der bisher bekannten Halogenate von Erdalkalimetallen werden im Hinblick auf die energetische (Schwingungsfrequenzen) und geometrische (Bindungslängen) Verzerrung der XO3--Ionen sowie der Stärke der Wasserstoffbrücken diskutiert.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19926080220
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  • 9
    Electronic Resource
    Electronic Resource
    Verfeinerung der Kristallstruktur von K2O2 (1992)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 610 (1992), S. 64-66 
    Details
    ISSN: 0044-2313
    Keywords: Dipotassium peroxide ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Refinement of the Crystal Structure of K2O2The crystal structure of K2O2 has been refined using 241 diffractometer data (Cmca; a = 6.733(1), b = 6.996(1), c = 6.474(1) Å; Z = 4; Rw = 0.050). The distance O—O (1.541(6) Å) is significantly larger than that one assumed for alkali metal peroxides, so far.
    Notes: Die Kristallstruktur von K2O2 wurde auf der Basis von Vierkreisdiffraktometerdaten (241 unabhängige Strukturfaktoren) verfeinert (Cmca; a = 6,733(1), b = 6,996(1), c = 6,474(1) Å; Z = 4; Rw = 0.050). Der gefundene O—O-Abstand weist mit 1,541(6) Å einen deutlich größeren Wert auf als bisher für die Alkalimetallperoxide angenommen.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19926100111
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  • 10
    Electronic Resource
    Electronic Resource
    Strukturchemische Verwandtschaft von Kaliumhexahydroxoscandat(III), K3[Sc(OH)6] mit den isotypen Hydroxometallaten Rb3[Sc(OH)6], K3[Cr(OH)6] und Rb3[Cr(OH)6]Professor Rudolf Hoppe zum 70. Geburtstage gewidmet (1992)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 616 (1992), S. 71-78 
    Details
    ISSN: 0044-2313
    Keywords: Potassium hexahydroxoscandate ; rubidium hexahydroxoscandate ; rubidium hexahydroxochromate ; structure determination ; crystal chemistry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Structural Relationship of Potassium Hexahydroxoscandate(III), K3[Sc(OH)6] with the Isotypic Hydroxometallates Rb3[Sc(OH)6], K3[Cr(OH)6], and Rb3[Cr(OH)6]Ternary hydroxides M3I}MIII(OH)6{ with MI = K, Rb and MIII = Sc, Cr were obtained in the same way as K3[Cr(OH)6] [1] from alkali metal amides and d-metal nitrates by a comproportionation reaction of amide and nitrate ions in supercritical ammonia to elementary nitrogen and hydroxide ions at 523 K and 3 ≤ p(NH3) ≤ 6 kbar within 1 to 3 months. Their structures were determined by single crystal x-ray methods inclusive the positions of the hydrogen atoms. The ratio of size of r(MI)/r(MIII) is related to the symmetry of these hydroxometallates. Structural relationships between K3[Sc(OH)6] and Rb3[Sc(OH)6], K3(Cr(OH)6], Rb3[Cr(OH)6]) and K4[CdCl6] [4] are discussed.
    Notes: Ternäre Hydroxide M3I{MIII(OH)6}mit MI = K, Rb und MIII = Sc, Cr wurden analog zu K3[Cr(OH)6] [1] aus Alkalimetallamiden und d-Metallnitraten durch Komproportionierung von Amid- und Nitrationen zu elementarem Stickstoff und Hydroxidionen in überkritischem Ammoniak bei 523 K und 3 ≤ p(NH3) ≤ 6 kbar innerhalb von 1 bis 3 Monaten dargestellt. Die Atomanordnungen der Verbindungen wurden einschließlich der H-Positionen röntgenographisch an Einkristallen bestimmt. Das Größenverhältnis r(MI)/r(MIII) korreliert mit der Symmetrie dieser Verbindungen. Strukturchemische Beziehungen von K3[Sc(OH)6 zu Rb3[Sc(OH)6], K3[Cr(OH)6], Rb3[Cr(OH)6] zu K4[CdCl6] [4] werden diskutiert.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19926161012
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