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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 8364-8370 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 7748-7761 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The region of the potential energy surface for the title reaction in the vicinity of its minimum energy path has been predicted from the analysis of ab initio electronic energy calculations. The ab initio procedure employs a 6–31G** basis set and a configuration interaction calculation which uses the orbitals obtained in a generalized valence bond calculation. Calculated equilibrium properties of ethane and of isolated methyl radical are compared to existing theoretical and experimental results. The reaction coordinate is represented by the carbon–carbon interatomic distance. The following attributes are reported as a function of this distance and fit to functional forms which smoothly interpolate between reactant and product values of each attribute: the minimum energy path potential, the minimum energy path geometry, normal mode frequencies for vibrational motion orthogonal to the reaction coordinate, a torsional potential, and a fundamental anharmonic frequency for local mode, out-of-plane CH3 bending (umbrella motion). The best representation is provided by a three-parameter modified Morse function for the minimum energy path potential and a two-parameter hyperbolic tangent switching function for all other attributes. A poorer but simpler representation, which may be satisfactory for selected applications, is provided by a standard Morse function and a one-parameter exponential switching function. Previous applications of the exponential switching function to estimate the reaction coordinate dependence of the frequencies and geometry of this system have assumed the same value of the range parameter α for each property and have taken α to be less than or equal to the "standard'' value of 1.0 A(ring)−1. Based on the present analysis this is incorrect: The α values depend on the property and range from ∼1.2 to ∼1.8 A(ring)−1.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 11 (1968), S. 0 
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Results of X-ray textural studies of dolomite and the clay minerals in the Marl Slate and of siderite from the top of the Mansfield Marine Band are interpreted in terms of the possible diagenetic development of the re-crystallized carbonates in these two rocks. From computer processed (1014) fabrics of the two trigonal carbonates it is deduced that there is a c-axis preferred orientation concordant with the normal to the stratification. An early diagenesis in this oriented mode must be a function of both a threshold stress difference in a non-hydrostatic stress field (in effect a necessary minimum depth of burial) and also of the presence of connate solutions. The existance of a minor percentage of dolomite oriented with the rhomb faces parallel to the stratification probably reflects an even earlier crystallization within the top few metres of sediment, when the confining pressures and pressure differences were of insignificant amplitude. It is concluded that a higher rate of sedimentation associated with the Coal Measure sequence is responsible for the singular preferred orientation of the siderite.
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 205 (1965), S. 793-793 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 204 (1964), S. 175-176 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The occurrence of pyrrhotite in the northern Pennine orefield6, although limited, is of interest because fluid inclusion studies have shown that depositional temperatures of fluorito and quartz, the two most abundant minerals in the central portions of the field, are below 250 C. To our knowledge ...
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 20 (1971), S. 292-298 
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract INDO-MO Calculations have been carried out on the anions of a variety of pyridine derivatives for which e.s.r. data have recently become available. The method gives reasonable results for proton hyperfine splitting constants but calculated nitrogen splitting constants are considerably larger than the experimental values. Some π-only calculations are included for the pyridine anion. All methods overestimate the spin density at the nitrogen atom. The orbital populations and excess charges for the pyridine molecule are not in agreement with those of an ab initio calculation.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 16 (1970), S. 55-62 
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Für die Grundzustände der Moleküle O2 und NO werden lokalisierte Orbitale abgeleitet, indem die Lokalisierungsmethoden getrennt für die Orbitale mitα- undβ-Spin angewendet werden. Dabei werden sowohl die eigentlichen Energielokalisierungsmethoden als auch die gleichförmigen Lokalisierungsmethoden benutzt. Die erhaltenen lokalisierten Orbitale stimmen gut mit den von Linnett vorgeschlagenen Formeln überein.
    Abstract: Résumé Obtention d'orbitales localisées pour l'état fondamental des molécules d'oxygène et d'oxyde nitreux par localisation indépendante des orbitales de spinα et des orbitales de spinβ. Emploi simultané de la localisation selon l'énergie intrinsèque et de la localisation uniforme. Les orbitales localisées résultantes sont en bon accord avec les formules suggérées par Linnett.
    Notes: Abstract Localized orbitals are derived for the ground states of the oxygen and nitric oxide molecules by applying localization methods separately to the orbitals containing electrons of alpha- and betaspin. Both the intrinsic energy localization and the uniform localization methods are used. The resulting localized orbitals are in good agreement with the formulae suggested by Linnett.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 23 (1972), S. 378-382 
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The results of INDO-MO calculations of hyperfine splitting constants for the radical-anions of a series of styrene derivatives are presented. The calculations reproduce the general features of the observed e.s.r. spectra but the detailed agreement is less good than that of previously reported McLachlan calculations.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 26 (1972), S. 179-186 
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The calculation of non-paired spatial orbitals and alternant molecular orbital wavefunctions for the benzyl radical is described. The NPSO and AMO methods give comparable energy lowerings which indicate that they make substantial allowance for electron correlation. The calculated spin densities are not in very good accord with experiment and it is thought that this reflects inadequacies in the integral approximations used.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 22 (1971), S. 315-324 
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Methode der ungepaarten räumlichen Orbitale (NPSO) wird auf das π-Elektronensystem des Naphthalins und des Azulens angewendet. Die Berechnungen werden ohne Spinprojektion durchgeführt; die Tripletkomponente wird beseitigt. Die Methode führt zu einer bedeutenden Verringerung der Energie für beide Moleküle; für Azulen ergibt die NPSO-Funktion mit einem Parameter ähnliche Ergebnisse wie mit der weit aufwendigeren Methode der alternierenden Molekülorbitale. Es wird eine Form der NPSO-Wellenfunktion vorgeschlagen, die mit geringem Aufwand benutzt werden kann. Es wird gezeigt, daß die NPSO-Wellenfunktion für die genannten Moleküle mit Hilfe eines Parameters dargestellt werden kann, der aus Berechnungen an kleineren Systemen stammt.
    Notes: Abstract The method of non-paired spatial orbitals (NPSO) is applied to the π-electron systems of naphthalene and azulene. Calculations are made without spin projection and with the annihilation of the triplet component. The method leads to a substantial lowering of the energy for both molecules and for azulene the one parameter NPSO function gives results similar to the much more complicated alternant molecular orbital method. A form of NPSO wavefunction which can be used with modest effort is proposed. It is shown that the NPSO wavefunctions for these molecules can be reasonably written using a parameter deduced from calculations on smaller systems.
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