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  • 1
    Electronic Resource
    Electronic Resource
    A molecular dynamics simulation of crystalline α-cyclodextrin hexahydrate (1987)
    Springer
    European biophysics journal 15 (1987), S. 197-210 
    Details
    ISSN: 1432-1017
    Keywords: α-cyclodextrin hexahydrate ; molecular dynamics simulation ; empirical force field ; hydrogen bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The structure of crystalline α-cyclodextrin (α-CD) hexahydrate, form I (C36H60O30·6H2O, space group P212121) is experimentally so well determined by X-ray and by neutron diffraction analyses that the positions of all the hydrogen atoms are available. This provides an opportunity for testing an empirical force field that is currently used in simulations of protein and nucleic acid structures by performing molecular dynamics studies employing the GROMOS program package on a system of 4 unit cells containing 16 α-CD molecules and 96 water molecules. A detailed comparison of the simulated and experimentally determined crystal structures shows that the experimental positions of the α-CD atoms are reproduced within 0.025 nm, well within the overall experimental accuracy of 0.036 nm; that the water molecules are on average within 0.072 nm from their experimental sites, with two thirds reproduced within experimental accuracy by the calculations; that high correlation is produced, between the occurrence of simulated and experimentally observed hydrogen bonds. The good agreement between simulated and experimental results suggests that the tested force field is reliable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00577068
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of crystalline β-cyclodextrin dodecahydrate at 293 K and 120 K (1987)
    Springer
    European biophysics journal 15 (1987), S. 211-224 
    Details
    ISSN: 1432-1017
    Keywords: β-cyclodextrin dodecahydrate ; molecular dynamics simulation ; hydrogen bonds ; empirical force field ; water molecule diffusion ; positional disorder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Molecular dynamics (MD) simulations for crystalline β-cyclodextrin dodecahydrate (β-CD) at two different temperatures, 293 K and 120 K, have been performed using the GROMOS program package. The calculated structural properties are compared to those obtained from neutron diffraction studies of this system at the quoted temperatures. The simulation was carried out over a period of 20 ps on four unit cells containing 8 β-CD molecules and 96 water molecules, whereby all atoms were allowed to move. At room temperature, the experimental positions of the (non-hydrogen) glucose atoms are reproduced within 0.034 nm, a value which is smaller than the experimental (0.041 nm) or simulated (0.049 nm) overall root mean square (rms) positional fluctuation. The corresponding numbers for the low temperature study are 0.046 nm, 0.019 nm and 0.022 nm. At both temperatures the experimentally observed degree of anisotropy of the atomic motions is also found in the simulations. The comparison of a variety of structural properties leads to the conclusion that the molecular model and force field used are able to simulate the cyclodextrin system very well. Experimentally observed differences in properties as a function of number of glucose units in the CD molecule (α-CD, 6 versus β-CD, 7) and as a function of temperature are qualitatively reproduced by the simulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00577069
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  • 3
    Electronic Resource
    Electronic Resource
    Industrielle Anorganische Chemie Von W. Büchner R. Schliebs G. Winter und K. H. Büchel Verlag Chemie, Weinheim 1984.XXIII, 645 S., geb. DM 108.00  - ISBN 3-527Y26069-2 (1986)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 98 (1986), S. 113-113 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19860980134
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  • 4
    Electronic Resource
    Electronic Resource
    Darstellung, Strukturen und Eigenschaften von SmBeF4 und SrBeF4  -  ungewöhnliche Varianten der BarytstrukturIn memoriam Professor Wilhelm Klemm (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 179-186 
    Details
    ISSN: 0044-2313
    Keywords: Strontium beryllium tetrafluoride ; samarium beryllium tetrafluoride ; structure ; divalent Samarium ; luminescence ; magnetism ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation, Structures, and Properties of SmBeF4 and SrBeF4 - Unusual Variants of the Baryt Type StructureSmBeF4 has been obtained as orange-yellow crystals and SrBeF4 as colourless crystals while heating mixtures of SmF3, Sm-powder, BeF2 (2 : 1 : 3) and SrF2 and BeF2 (1 : 1), respectively, under Ar after 7-10 d at about 700°C. SmBeF4 crystallizes in Pna21 (No. 33) with a = 846.1(5), b = 676.9(5), c = 524.1(4) pm and SrBeF4 in P21/n (Nr. 14) with a = 529.5(5), b = 830.9(2), c = 678.8(4) pm and β = 90.0°.The structures of SmBeF4 and the room temperature modification of SrBeF4 are related to the baryt type structure. The differences to the structure BaSO4 are mutual rotations of the BeF4 tetrahedra and their shift with respect to the Sm and Sr framework, respectively. According to the refinement of the structure of SmBeF4 at -174°C these effects are enhanced at low temperatures. SmBeF4 exhibits sharp luminescence lines at around 690nm. Measurements of the magnetic susceptibility show the temperature dependence typically found for Sm2+. The Madelung parts of the lattice energy for SmBeF4 und SrBeF4 have been calculated and discussed.
    Notes: Orangegelbe Kristalle von SmBeF4 und farblose Kristalle von SrBeF4 wurden durch Erhitzen entsprechender Gemenge von SmF3, Sm-Pulver, BeF2 (2 : 1 : 3) bzw. SrF2 und BeF2 (1 : 1) unter Ar nach 7-10 d bei ca. 700°C erhalten. SmBeF4 kristallisiert in Pna21 (Nr. 33) mit a = 846,1(5), b = 676,9(5), c = 524,1(4) pm und SrBeF4 in P21/n (Nr. 14) mit a = 529,5(5), b = 830,9(2), c = 678,8(4) pm und β = 90,0°.Die Strukturen von SmBeF4 und der Raumtemperaturmodifikation von SrBeF4 sind mit dem Baryttyp verwandt. Die Unterschiede zur Barytstruktur bestehen in gegenseitigen Verdrehungen der BeF4-Tetraeder und deren Verschiebung gegenüber dem Sm- bzw. Sr-Teilgerüst. Die Bestimmung der Tieftemperaturstruktur von SmBeF4 (-174°C) zeigt eine Verstärkung die ser Effekte. SmBeF4 zeigt die für Sm2+ charakteristischen intensiven Lumineszenzbanden bei etwa 690 nm sowie eine für Sm2+ typische Temperaturabhängigkeit der magnetischen Suszeptibilität. Die Madelunganteile der Gitterenergie für SmBeF4 und SrBeF4 wurden berechnet und diskutiert.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966220126
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  • 5
    Electronic Resource
    Electronic Resource
    Na3Al2Nb34O64 und Na (Si, Nb) Nb10O19: Clusterverbindungen mit isolierten Nb6-OktaedernProfessor Rudolf Hoppe zum 65. Geburtstage am 29. Oktober 1987 gewidmet (1987)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 553 (1987), S. 106-122 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Na3Al2Nb34O64 and Na (Si, Nb) Nb10O19. Cluster Compounds with Isolated Nb6-OctahedraHexagonal ormolu coloured plates of the new compounds Na3Al2Nb34O64 (I) and Na(Si, Nb)Nb10O19 (II) were prepared by heating pellets of NaF, Al2O3, NbO2 and NbO (3:1:8:2) and NaF, NbO2 and NbO (1:4:2), respectively, at approx. 850°C. I was contained in a sealed gold capsule, II in a silica tube. The Si incorporated in II originates from the container material. Both compounds crystallize in R 3, I with a = 784.4(1), c = 7065(1) pm, Z = 3 and II with a = 784.1(1), c = 4221.8(5) pm, Z = 6. I and II represent new structure types. They contain the same characteristic structural units, namely discrete Nb6O12 clusters (dNb-Nb = 283 ± 4 pm) and Nb2O10 units with Nb-Nb dumbells (dNb-Nb ≍ 269 pm) in edgesharing coordination octahedra. In addition NbO6 octahedra containing Nb in the oxidation state + 5 and NaO12 cube-octahedra occur in both compounds besides AlO4 and SiO4 tetrahedra in I and II, respectively. The structures can be described in terms of a common closepacking of O and Na atoms together with Nb6 octahedra.
    Notes: Hexagonale, altgoldfarbene PlättChen der neuen Verbindungen Na3Al2Nb34O64 (I) bzw. Na(Si, Nb) Nb10O19 (II) wurden durch Erhitzen von zu Pillen gepreßten Gemengen aus NaF, Al2O3, NbO2 und NbO (3:1:8:2) bzw. NaF, NbO2 und NbO (1:4:2) bei etwa 850°C dargestellt. I war in einem geschlossenen Au-Rohr, II in einer Quarzampulle eingeschlossen; das in II eingebaute Si stammt aus der Gefäßwand. Beide Verbindungen kristallisieren in R 3, I mit a = 784,4(1), c = 7065(1) pm und Z = 3, II mit a = 784,1(1), c = 4221,8(5) pm und Z = 6.I und II bilden jeweils einen neuen Strukturtyp. Beide enthalten als charakteristische Baugruppen diskrete Nb6O12-Cluster (dNb-Nb = 283 ± 4pm) sowie Nb2O10-Einheiten mit Nb-Nb-Paaren (dNb-Nb ≍ 269 pm) und kantenverknüpften Koordinationsoktaedern. Ferner liegen NbO6-Oktaeder mit Nb in der Oxidationsstufe + 5, und NaO12-Kuboktaeder sowie in I AlO4-bzw. in II SiO4-Tetraeder vor. Die Strukturen lassen sich mit gemeinsam dichten Packungen von O-Atomen, Na-Atomen und Nb6-Oktaedern beschreiben.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19875531013
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  • 6
    Electronic Resource
    Electronic Resource
    LiSmAlF6  -  das erste Fluoroaluminat mit zweiwertigem Samarium (1991)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 606 (1991), S. 169-176 
    Details
    ISSN: 0044-2313
    Keywords: Lithium samarium hexafluoroaluminate ; preparation ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: LiSmAlF6  -  the First Fluoroaluminate with Divalent SamariumLiSmAlF6, the first quaternary fluoride with Sm2+ that has been obtained as red transparent single crystals, is formed while heating corresponding mixtures of the starting materials in niobium or tantalum crucibles under argon after 7-10 d at about 800°C. Orange-red, microcrystalline powder samples of LiSmAlF6 could be prepared at T ≤ 700°C after 1-2 d under the same conditions.LiSmAlF6, crystallizes as a new structure type in P6322 (Nr. 182) with a = 507.9(1), c = 1 040.5(1) pm and Z = 2 (CAD4, 2 512 Io, Rw = 2,3%). The crystal structure of LiSmAlF6 is related to the LiCaAlF6 structure type whereby the essential difference lies in the coordination of the M2+ ions. Ca2+, as well as Sr2+ in LiSrAlF6, exhibit octahedral coordination, whereas Sm2+ has, surprisingly, trigonal prismatic coordination to F-. The two triangles of the SmF6 prism are twisted by 8.3° with respect to each other.Measurements of the magnetic susceptibility show the temperature dependence typically found for Sm2+. The Madelung part of the lattice energy has been calculated and is discussed.
    Notes: LiSmAlF6, das erste in Form roter, transparenter Einkristalle erhaltene quaternäre Fluorid mit Sm2+, bildet sich beim Erhitzen geeigneter Ausgangsmenge in Niob- oder Tantaltiegln unter Ar nach 7-10 d bei ca. 800°C. Orangerote, mikrokristalline Pulverproben von LiSmAlF6 können bei T ≤ 700°C bereits nach 1-2 Tagen unter sonst gleichen Bedingungen dargestellt werden.LiSmAlF6 kristallisiert in einem neuen Strukturtyp in P6322 (Nr. 182) mit a = 507,9(1), c = 1 040,5(1) pm und Z = 2(CAD4, 2 512 Io, Rw = 2,3%). Die Kristallstruktur von LiSmAlF6 ist dem LiCaAlF6-Typ verwandt, zeigt aber den wesentlichen Unterschied in der Umgebung für M2+ : Ca2+, wie auch Sr2+ in LiSrAlF6, werden oktaedrisch, Sm2+ jedoch überraschenderweise trigonal-prismatisch von F- koordiniert. Die beiden Dreiecke des SmF6-Prismas sind um 8,3° gegeneinander verdreht.Messungen der magnetischen Suszeptibilität zeigen die für Sm2+ typische Temperaturabhängigkeit. Der Madelunganteil der Gitterenergie wurde berechnet und diskutiert.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19916060117
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  • 7
    Electronic Resource
    Electronic Resource
    High resolution electron microscopy studies of Ba4Nb14O23Dedicated to Professor Harald Schäfer on his 80th Birthday (1993)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 133-137 
    Details
    ISSN: 0044-2313
    Keywords: Barium niobium oxide, Ba4Nb14O23 ; cluster ; electron microscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Untersuchungen an Ba4Nb14O23 mittels hochauflösender Elektronenmikroskopie.Die neue Verbindung Ba4Nb14O23, wurde durch Tempern von Gemengen von Ba5Nb4O15, Nb2O5 und Nb bei 1 450°C unter Ar erhalten. Ba4Nb14O23 wurde durch Untersuchungen mittels hochauflösender Elektronenmikroskopie und Röntgenpulveruntersuchungen charakterisiert. Die Verbindung kristallisiert orthorhombisch C-zentriert mit a=20.782(4), b=12.448(3), c=4.147(1) Å und Z=2. Die Kristallstruktur von Ba4Nb14O23 kann als intergrowth zwischen BaNbO3 und NbO beschrieben werden. Charakteristische Baueinheiten sind Dreierketten spitzenverknüpfter Nb6-Oktaeder, die über Stränge perowskitartiger Baugruppen zu einem dreidimensionalen Netzwerk verknüpt sind.
    Notes: The new compound, Ba4Nb14O23, has been prepared by heating mixtures of Ba5Nb4O15, Nb2O5 and Nb at 1 450°C under Ar. Ba4Nb14O23 has been studied by means of high resolution electron microscopy and X-ray powder diffraction techniques. It has a C-centered orthorhombic unit cell with a=20.782(4), b=12.448(3), c=4.148(1) Å and Z=2. The structure of Ba4Nb14O23 can be considered as being an intergrowth between BaNbO3 and NbO. Characteristic building units are triple chains of corner sharing Nb6 octahedra which are connected via columns of the perovskite type structure to a three dimensional network.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19936190122
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  • 8
    Electronic Resource
    Electronic Resource
    Über das neue gemischtvalente Ge7F16: [GeF6]2--Oktaeder zwischen [Ge6F10]2+-Schichten - zur stereochemischen Aktivität freier Elektronenpaare (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 596-602 
    Details
    ISSN: 0044-2313
    Keywords: Germanium fluoride ; stereochemical activity ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: About the New Mixed Valent Ge7F16: [GeF6]2- Octahedra between [Ge6F10]2+ Sheets - a Contribution to the Stereochemical Activity of Lone PairsFor the first time Ge7F16 colourless transparent single crystals have been prepared by the reduction of GeF4 with Ge at 300°C. The extremely hygroscopic fluoride crystallizes in a new structure type in Cc with a = 1818.0(6) pm, b = 754.3(2) pm, c = 1030.4(3) pm, β = 90.33(3)° und Z = 4.Ge7F16 is a mixed valent fluoride according to 6GeF2 × GeF4. Characteristical building units of the new structure type are [Ge6F10]2+ sheets, which are connected via [GeF6]2- octahedra. The Ge2+ within the sheets are coordinated by three nearest F- with distances of 183-218 pm and together with these form distorted trigonal pyramids. The structure of Ge7F16 can be considered as a member of the homologues series Gem4+Gen2+F4m+2n with m = 1 and n = 6. Bond order summations, band structure calculations and calculations of the Madelung part of the lattice energy. MAPLE, have been used for the discussion of the bonding situation.
    Notes: Neu dargestellt wurden farblose transparente Einkristalle von Ge7F16 durch Reduktion von GeF4 mit Ge bei 300°C. Das äußerst hygroskopische Fluorid kristallisiert in einem neuen Strukturtyp in der Raumgruppe Cc (Nr. 9) mit a = 1818.0(6) pm, b = 754.3(2) pm, c = 1030.4(3) pm, β = 90.33(3)° und Z = 4.Ge7F16 ist gemäß 6GeF2 × GeF4 ein gemischtvalentes Fluorid. Charakteristische Baugruppen des neuen Strukturtyps sind [Ge6F10]2+-Schichten, die über [GeF6]2--Oktaeder verbrückt sind. Die Ge2+ innerhalb der Schichten sind von je drei nächsten F- im Abstand von 183-218 pm koordiniert und bilden mit diesen verzerrte trigonale Pyramiden. Die Struktur von Ge7F16 läßt sich als Glied der homologen Reihe Gem4+Gen2+F4m+2n mit m = 1 und n = 6 beschreiben. Die Bindungsverhältnisse werden anhand von Bindungsordnungssummationen, Bandstrukturrechnungen und Berechnungen des Madelunganteils der Gitterenergie, MAPLE. diskutiert.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19976230193
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  • 9
    Electronic Resource
    Electronic Resource
    SmAlF5  -  ein neues SmII-fluoroaluminat mit Al2F10-Oktaederdoppeln und [AlF2/2F4/1]-Ketten (1993)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 181-188 
    Details
    ISSN: 0044-2313
    Keywords: Samarium(II) fluoroaluminate ; preparation ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: SmAlF5  -  a New Samarium(II) Fluoroaluminate with Al2F10 Bioctahedra and [AlF2/2F4/1] Chains.SmAlF5 has been obtained as orange-red transparent single crystals while heating mixtures of SmF3, Sm-powder and AlF3 (2:1:3) in a niobium crucible under Ar after 7-10 d at about 750°C. SmAlF5 crystallises in I 4/m (Nr. 87) with a=1 414.4(4), c=722.2(3) pm and Z=8 (CAD4, 4 340 IO, Rw=1.7%).The crystal structure of SmAlF5 is isotypic to BaTiF5. Characteristic building units are linear chains of trans-corner sharing AlF6 octahedra, which are connected via corners to two further AlF6 octahedra. Isolated Al2F10 octahedra lie disordered between such chains. The Sm atoms connect the AlF6 octahedra to a three-dimensional network. Measurements of the magnetic susceptibility show the temperature dependence typically found for Sm2+. The Madelung part of the lattice energy has been calculated and is discussed.
    Notes: SmAlF5 wurde in Form orangeroter transparenter Einkristalle beim Erhitzen von SmF3, Sm-Pulver und AlF3 (2:1:3) im Niobtiegel unter Ar nach 7-10 d bei ca. 750°C erhalten. SmAlF5 kristallisiert in I4/m (Nr. 87) mit a=1 414,4(4), c=722,2(3) pm und Z=8 (CAD4, 4 340 IO, Rw=1,7%).Die Kristallstruktur von SmAlF5 ist isotyp zu BaTiF5. Charakteristische Baugruppen sind lineare Ketten trans-Spitzen verknüpfter AlF6-Oktaeder, die über Spitzen mit zwei weiteren AlF6-Oktaedern verknüpft sind. Isolierte Al2F10-Oktaederdoppel liegen fehlgeordnet zwischen solchen Ketten. Die Sm-Atome verknüpfen die AlF6-Oktaeder zum dreidimensionalen Gerüst. Messungen der magnetischen Suszeptibität zeigen die für Sm2+ typische Temperaturabhängigkeit. Der Madelunganteil der Gitterenergie wurde berechnet und diskutiert.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19936190130
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  • 10
    Electronic Resource
    Electronic Resource
    NaNb10O18 - ein neues Oxoniobat mit [Nb6O12]-Clustern (1989)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 572 (1989), S. 7-17 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: NaNb10O18-a New Oxoniobate with [Nb6O12]-ClustersGolden reflecting single crystals and black powders of NaNb10O18 have been prepared by heating a mixture of NaNbO3, NbO, NbO2 and B2O3 (as mineralizer) at 900°C. The compound crystallizes in P21/c with a = 784.9(5), b = 931.6(4), c = 1028.1(3) pm, β = 110.53(4) und Z = 2 in a new structure type.The crystal structure is formed from common close packed sheets of O atoms, Na atoms and Nb6 octahedra. Characteristic building groups are NbO6 octahedra (Nb5+) and Nb6O12 clusters with short distances dNb—Nb = 277-288 pm. The number of valence electrons per Nb6O12 cluster is 15 or 14 assuming that one electron belongs to the four Nb5+ atoms. Extended Hückel calculations, metallic conductivity and Pauli type paramagnetism however would favour the model of one delocalized electron per formula unit according to (the formal description) Na+(Nb6)16+(Nb4)20+(O18)36-e-. The Madelung part of the lattice energie (MAPLE) has been calculated and discussed.
    Notes: NaNb10O18 wurde in Form goldgelber Einkristalle und schwarzer Pulver durch Tempern eines Gemenges aus NaNbO3, NbO und NbO2 sowie B2O3 (als Mineralisator) bei 900°C dargestellt. Die Verbindung kristallisiert in P21/c mit a = 784,9(5), b = 931,6(4), c = 1 028,1(3) pm, β = 110,53(4)° und Z = 2 in einem neuen Strukturtyp.Die Kristallstruktur besteht aus gemeinsam dicht gepackten Schichten von O-Atomen, Na-Atomen und Nb6-Oktaedern. Neben NbO6-Oktaedern (Nb5+) liegen charakteristische Nb6O12-Cluster mit kurzen Abständen dNb—Nb = 277-288 pm vor. Die Zahl der Valenzelektronen pro Nb6O12-Cluster beträgt 15 oder 14, wenn man ein Elektron den vier Nb5+-Atomen in den NbO6-Oktaedern zuordnet. Extended-Hückel-Rechnungen, metallische Leitfähigkeit und Pauli-Paramagnetismus weisen aber eher auf ein delokalisiertes Elektron pro Formeleinheit gemäß (der sehr formalen Schreibweise) Na+(Nb6)16+(Nb4)20+(O18)36-e- hin. Der Madelunganteil der Gitterenergie (MAPLE) wurde ebenfalls berechnet und diskutiert.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19895720102
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