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  • Crystal Structure  (40)
  • Computational Chemistry and Molecular Modeling  (12)
  • 1
    Electronic Resource
    Electronic Resource
    Construction of linearly independent relativistic symmetry orbitals for finite double-point groups including time reversal symmetry (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 445-465 
    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: A formalism is developed for the construction of relativistic symmetry-adapted molecular basis functions under consideration of time reversal invariance. The theory is applicable to the finite double point groups Cn, Cnh, Sn, Cnv, Dn, Dnd, Dnh, T, Th, Td, O, and Oh. It is based on the LCAO method. A projection operator technique is employed to construct molecular symmetry orbitals from atomic orbitals. The search for linearly independent basis function is simplified by means of group theoretical considerations.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560330505
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular mechanics of organic halides. III. Fluorinated olefins (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 111-117 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A molecular mechanical force field for fluorinated ethylenes and propylenes is described. The field computes geometries, dipole moments, and energy differences between isomers and rotamers. Component analysis indicates that “classical” strains alone (skeletal, nonbonded, electrostatic) cannot account for energy relationships. The discussion is supplemented by a semiempirical quantum chemical comparison of cis- and trans-FCH=CHF and of gauche- and anti-FCH2CH2F.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540010202
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  • 3
    Electronic Resource
    Electronic Resource
    Towards the convergence of molecular-mechanical force fieldsOriginal proofs for this paper were delayed in the mail. (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 6 (1985), S. 1-4 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: It is noticed that inclusion of an electrostatic term in the molecular-mechanical treatment of hydrocarbons would compel the nonbonding parameters of different force fields to become more alike than they are at present. Apart from removing the discontinuity in passing from the calculation of an unfunctionalized parent compound to the calculation of its functionalized derivatives, it is expected that the inclusion would improve results for the hydrocarbons themselves.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540060102
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular mechanics and molecular shape. V.For Part IV, see Ref. 1. on the computation of the bare surface area of molecules (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 9 (1988), S. 18-24 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: This article examines the numerical estimation of molecular surface areas within the model of overlapping atomic spheres. One has the choice of either basing the estimate on all elements that contribute to the surface, or of ignoring systematically some elements in the interatomic clefts. It is argued that the second choice, even though more approximate, implicitly improves on the model and is to be preferred. Since surface areas are not measurable, the demonstration is unavoidably roundabout, relying mostly on correlation analysis. Among the regressors occur two compounded parameters. One, ratio of the surface area of the equivalent sphere to the surface area, is interpreted as a measure of molecular globularity. It reflects the molecular axis-ratio and surface convolution. The other, ratio of the surface area to the volume, is interpreted as a measure of the global congestion of a chemical residue. Together with a measure of the local congestion at the point of attachment, it affects the steric hindrance that a residue offers. The relation between the surface area and the number of valence electrons is also discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540090104
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  • 5
    Electronic Resource
    Electronic Resource
    Construction of linearly independent relativistic symmetry orbitals for finite double-point groups including time reversal symmetry (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 1369-1372 
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520611
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  • 6
    Electronic Resource
    Electronic Resource
    Electron correlation effects in target molecule in low-energy e- + N2 scattering (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 55 (1995), S. 291-297 
    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: In this article, we discuss how to incorporate correlation aspects in the interaction of the electron with a “frozen” correlated target. We discuss the important aspects of correlation for e- + N2 scattering using configuration interaction, coupled cluster, and perturbative methods to describe the correlation in the target molecule. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560550311
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  • 7
    Electronic Resource
    Electronic Resource
    Synthese und Struktur der ersten Wasserfreien ternären Lithiumnitrate der Lanthanide, Li2[M(NO3)5] (M = La, Pr—Eu) (1993)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 513-516 
    Details
    ISSN: 0044-2313
    Keywords: Synthesis ; Crystal Structure ; Lanthanides ; Ternary Lithium Nitrates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Structure of the First Anhydrous Ternary Lithium Nitrates of the Lanthanides, Li2[M(NO3)5] (M = La, Pr—Eu).Single crystals of the ternary lithium nitrates of the lanthanides, Li2[M(NO3)5] (M = La, Pr—Eu), are obtained by dissolving the respective anhydrous nitrate, previously obtained by dehydration of M(NO3)3 · 6 H2O at 180°C under vacuum, in a melt of LiNO3. In the crystal structure of Li2[Pr(NO3)5] (orthorhombic, Pnnm, Z = 4, a = 899.6(2), b = 1 052.7(2), c = 1 178.6(2)pm; R = 0.072, Rw = 0.034) there are two crystallographically different Pr3+ ions, each surrounded by six bidentate nitrate ligands. One nitrate group is bridging between Pr1 and Pr2 resulting in a winded chain, ∞1[(O2/2NO2/1)Pr1(NO3)4(O2/2NO2/1)Pr2(O2/2NO2/1)(NO3)4]5-, running along [010]. The chains are packed hexagonally and held together by lithium ions. The coordination polyhydron of Li+ may be described as a bicapped trigonal prism.
    Notes: Einkristalle der ternären Nitrate der Lanthanide vom Typ Li2[M(NO3)5] (M = La, Pr—Eu) erhält man durch Auflösen der zuvor bei 180°C unter Vakuum entwässerten Hydrate M(NO3)3 · 6 H2O in einer Lithiumnitrat-Schmelze. Die Röntgenstrukturanalyse am Beispiel von Li2[Pr(NO3)5] (orthorhombisch, Pnnm, Z = 4; a = 899,6(2); b = 1 052,7(2); c = 1 178,6(2)pm; R = 0,072; Rw = 0,034) zeigt, daß zwei kristallographisch verschiedene Pr3+ vorliegen, die von jeweils sechs zweizähnigen Nitratliganden umgeben sind. Eine Nitratgruppe verbrückt zwischen Pr1 und Pr2, so daß sich eine gewundene Kette gemäß ∞1[(O2/2NO2/1)Pr1(NO3)4(O2/2NO2/1)Pr2(O2/2NO2/1)(NO3)4]5- ergibt, die längs [010] verläuft. Die Kettenstränge sind gemäß einer hexagonalen Stabpackung angeordnet und werden durch Li+-Ionen zusammengehalten. Die Koordination um Li+ kann als zweifach bekapptes trigonales Prisma beschrieben werden.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19936190313
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  • 8
    Electronic Resource
    Electronic Resource
    Cs4[Sc6C]Cl13 und Cs4[Pr6(C2)]I13  -  zwei Beispiele für das fehlende Bindeglied bei der Verknüpfung der Baueinheiten [M6Z]X12iX6aProfessor Horst Sabrowsky zum 60. Geburtstage gewidmet (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 1521-1526 
    Details
    ISSN: 0044-2313
    Keywords: Rare Earth Elements ; Halides ; Clusters ; Cesium Scandium Chloride Carbide ; Cesium Praseodymium Iodide Dicarbide ; Crystal Structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cs4[Sc6C]Cl13 and Cs4[Pr6(C2)]I13  -  Two Examples for the Missing Link in the Connectivity of [M6Z]X12iX6a Building UnitsCs4[Sc6C]Cl13 (tetragonal, I41/amd, a = 1 540.5(4), c = 1 017.9(7) pm, c/a = 0.661, Z = 4, R = 0.038, Rw = 0.026) and Cs4[Pr6(C2)]I13 (a = 1 804.9(3), c = 1 259.5(3) pm, c/a = 0.698, R = 0.106, Rw = 0.068) are obtained as green-black and blue-black single crystals with brass-like metallic lustre through metallothermic reduction of ScCl3 and PrI3, respectively, with cesium in the presence of carbon in sealed tantalum containers. The, overall, isotypic compounds contain isolated [Sc6C] and [Pr6(C2)] clusters, respectively, that are surrounded by 18 halide (X) ligands (12 Xi and 6 Xa; X = Cl or I). The connection is carried out via the motif [M6Z]X8iX4/21-aX4/2a-1X2/2a-a (M = Sc and Pr; Z = C and C2, respectively) and is thereby the missing link of the motifs of connection for the composition Ax[M6Z]X13. Analogous interconnection of [TiO6] octahedra is found in the anatase-type of structure of TiO2.
    Notes: Cs4[Sc6C]Cl13 (tetragonal, I41/amd; a = 1 540,5(4); c = 1 017,9(7) pm; c/a = 0,661; Z = 4; R = 0,038; Rw = 0,026 und Cs4[Pr6(C2)]I13 (a = 1 804,9(3); c = 1 259,5(3) pm; c/a = 0,698; R = 0,106; Rw = 0,068) werden bei der metallothermischen Reduktion von ScCl3 bzw. PrI3 mit Caesium in Gegenwart von Kohlenstoff in verschweißten Tantalampullen in Form von grünschwarzen bzw. blauschwarzen, messingglänzenden Einkristallen erhalten. Die weitgehend isotypen Kristallstrukturen enthalten isolierte [Sc6C]- bzw. [Pr6(C2)]-Cluster, die von 18 Halogenid-Ionen (X-, 12 Xi und 6 Xa; X = Cl bzw. I) umgeben sind. Die Verknüpfung erfolgt gemäß dem Motiv [M6Z]X8iX4/21-aX4/2a-1X2/2a-a (M = Sc bzw. Pr; Z = C bzw. C2) und stellt damit ein noch unbekanntes Verknüpfungsmuster für Verbindungen der Zusammensetzung Ax[M6Z]X13 dar, das jenem der [TiO6]-Oktaeder in der Anatas-Struktur von TiO2 entspricht.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19946200905
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  • 9
    Electronic Resource
    Electronic Resource
    Cs3[Tb10(C2)2]Cl21, ein neuer Formel- und Strukturtyp mit isolierten, dimeren Clustern (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 1527-1531 
    Details
    ISSN: 0044-2313
    Keywords: Terbium Cluster ; [Tb10(C2)2] ; Crystal Structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cs3[Tb10(C2)2]Cl21, A New Formula and Structure Type with Isolated Dimeric ClustersCs3[Tb10(C2)2]Cl21 is obtained via the metallothermic reduction of TbCl3 with caesium in the presence of graphite as black single crystals. The crystal structure (monoclinic, C2/c, Z = 4; a = 2318.72(13); b = 1245.8(9); c = 1502.0(13) pm; β = 98.13(6)°; R = 0.089; Rw = 0.049) contains dimeric clusters that are built from two octahedra connected via one common edge and filled with C2 units. These isolated [Tb10(C2)2] clusters are surrounded by 26 chloride ligands which are then connected via i - a and a - a bridges in a way that voids for Cs+ of coordination number 10 are formed.
    Notes: Cs3[Tb10(C2)2]Cl21 entsteht bei der metallothermischen Reduktion von TbCl3 mit Caesium in Gegenwart von Graphit in Form schwarzer Einkristalle. Die Kristallstruktur (monoklin, C2/c, z = 4; a = 2318,72(13); b = 1245,8(9); c = 1502,0(13) pm; β = 98,13(6)°; R = 0,089; Rw = 0,049) enthält dimere Cluster, die aus zwei über eine gemeinsame Kante verknüpften und durch zwei C2-Hanteln aufgefüllten Oktaedern gebildet werden. Die isolierten [Tb10(C2)2]-Cluster sind von insgesamt 26 Cl- umgeben und durch i - a- bzw. a - a-Brücken so miteinander verknüpft, daß für die Cs+ Lücken der Koordinationszahl 10 verbleiben.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19946200906
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  • 10
    Electronic Resource
    Electronic Resource
    Synthese und Kristallstruktur von NH4DyF4. Über weitere Fluoride NH4MF4 (M = La—Tb) (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 1393-1398 
    Details
    ISSN: 0044-2313
    Keywords: Rare Earth Fluorides ; Crystal Structure ; Ammonium Fluorides ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Crystal Structure of NH4DyF4. Further Fluorides NH4MF4 (M = La—Tb)
    Notes: Die Fluoride NH4MF4 (M = La—Dy) entstehen bei der Umsetzung der Metalle M mit N2H6F2 bei Temperaturen zwischen 80 und 350°C in verschweißten Monelampullen. Es werden in Abhängigkeit vom Selten-Erd-Element und von der Reaktionstemperatur drei Strukturen beobachtet: Die Kristallstruktur der Form I wurde anhand von Einkristallen von NH4DyF4 aufgeklärt [orthorhombisch, Pbcm (Nr. 57), Z = 4; a = 852,10(7) pm, b = 722,54(8) pm, c = 626,28(12) pm]; die bei niedrigen Temperaturen hergestellten Fluoride NH4MF4 (M = Ce—Tb) sind isotyp. Bei höheren Temperaturen treten die Formen II [für M = La—Nd; orthorhombisch (?), Z = 8] bzw. III [M = Eu—Tb, geordnete Überstruktur zum CaF2-Typ, analog TlGdF4, tetragonal, P4/m (?), Z = 16] auf.The fluorides NH4MF4 (M = La—Dy) are obtained through the reaction of the metals M with N2H6F2 at temperatures between 80 and 350°C in sealed Monel ampoules. Dependent upon the rare-earth element M and the reaction temperature three crystal structures are observed: The crystal structure of modification I was determined from single crystal data of NH4DyF4 [orthorhombic, Pbcm (no. 57), Z = 4; a = 852.10(7) pm, b = 722.54(8) pm, c = 626.28(12) pm]; the fluorides NH4MF4 (M = Ce—Tb) obtained at fairly low temperatures are isotypic. At higher temperatures the modifications II [for M = La—Nd; orthorhombic (?), Z = 8] and III [M = Eu—Tb, ordered superstructure of the CaF2 type, analogous to TlGdF4, tetragonal, P4/m (?), Z = 16] are observed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19976230913
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