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  • 1
    Electronic Resource
    Electronic Resource
    A comparison of lobe and cartesian gaussian basis sets for molecular calculations (1972)
    Springer
    Theoretical chemistry accounts 25 (1972), S. 49-53 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Lobe- und cartesische Gauß-Basissätze mit näherungsweise der gleichen Genauigkeit wie minimale Slater-Basissätze wurden für den Fall von Rechnungen an Molekülen verglichen. Die Basissätze wurden so konstruiert, daß sie nur in der Darstellung der Winkelabhängigkeit der p-Funktion voneinander abwichen. Berechnungen der Gesamtenergie und verschiedener Einelektron-Eigenschaften einer Serie von neuen Molekülen zeigen, daß “Lobe”- und cartesische Gaußrepräsentationen für Rechnungen an Molekülen äquivalent sind.
    Notes: Abstract Lobe gaussian and cartesian gaussian basis sets, of approximately minimal basis Slater accuracy, have been compared for molecular calculations. The basis sets were constructed so that they only differed in the representation of the angular dependence of the p function. Calculation of total energy and several one-electron properties for a series of nine molecules shows that, for molecular calculations, the lobe and cartesian gaussian representations are equivalent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00528258
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  • 2
    Electronic Resource
    Electronic Resource
    The electronic structure of the NF2 radical (1973)
    Springer
    Theoretical chemistry accounts 28 (1973), S. 339-353 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Ab intio-Rechnungen nach der uneingeschränkten Hartree-Fock-Methode (UHF-Methode) (mit und ohne einfache Auslöschung) wurden für das Radikal NF2 mit verschiedenen Basissätzen durchgeführt. Die vier Basissätze sind: ein minimaler Basissatz von Slaterfunktionen, zwei minimale Basissätze von Gaußfunktionen und ein größerer Satz von Gaußfunktionen von angenäherter Genauigkeit einer Doppelzeta-Basis. Der Vergleich der Basissätze bei der Berechnung von ladungsabhängigen Einelektron-Eigenschaften zeigt, daß der angenäherte Doppelzeta-Basissatz zur Berechnung geeigneter Werte notwendig ist. Eine einfache Auslöschung in den UHF-Wellenfunktionen, die mit den beiden Basissätzen mit genäherten Doppelzeta-2p-Funktionen berechnet wurden, führte auf eine genaue Darstellung der anisotropen Kopplungskonstanten am Stickstoff und an Fluor. Die Übereinstimmung der berechneten isotropen Kopplungskonstanten war bei allen Rechnungen weniger gut. Diese Ergebnisse für das NF2-Radikal zeigen, daß bei Verwendung einer geeigneten Basis mit Hilfe der UHF-Methode mit einfacher Auslöschung genaue Werte für die meisten von der Ladung oder vom Spin abhängigen Eigenschaften von Molekülen mit offenen Schalen gewonnen werden können.
    Notes: Abstract Ab initio unrestricted Hartree-Fock (UHF) calculations (with and without single annihilation) have been performed on the radical NF2 using four different basis sets; namely, a minimal basis Slater set, two minimal basis Gaussian sets and a Gaussian set of approximately double zeta accuracy. Several one-electron charge dependent properties have been calculated with each basis set and it is most apparent that near double zeta accuracy 2p functions are necessary to produce reliable values. Single annihilation of the UHF wavefunctions calculated with the two basis sets containing near double zeta 2p functions, was found to give an accurate representation of the anisotropic coupling constants at both the nitrogen and fluorine atoms. Less satisfactory agreement with the experimental isotropic coupling constants was found with all calculations. This investigation of the NF2 radical indicates that, providing a good quality basis set is used, the single annihilated UHF method can provide accurate values for most charge and spin dependent observable properties of open shell molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00529015
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  • 3
    Electronic Resource
    Electronic Resource
    Merged Gaussian lobe basis SCFMO calculations (1971)
    Springer
    Theoretical chemistry accounts 22 (1971), S. 214-223 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird über eine Methode berichtet, die Computerzeit bei Rechnungen mit Gaußfunktionbasissätzen wesentlich zu verkürzen, in dem man kleinere Sätze von Gaußfunktionen für die — und 4Zentren-Zweielektronenintegrale verwendet, dagegen die gesamte Basis für alle Einelektronen- und Ein- und Zweizentren-Zweielektronenintegrale. Die untersuchten Basissätze dieser Art gestatten eine gute Berechnung der Gesamtenergie und der Erwartungswerte einiger Elektronenoperatoren. Allerdings tritt eine größere Abweichung bei der Berechnung des Erwartungswertes für das Dipolmoment auf. Wenn sich die dargelegten Resultate als allgemeingültig erweisen, ist es fraglich, ob Berechnungen mit großen Gaußfunktionsbasissätzen, die ohne diese „Verschmelzungs“-Prozedur durchgeführt werden, einen Vorteil bieten, der die größeren Computerkosten rechtfertigt.
    Abstract: Résumé Description de calculs avec des bases gaussiennes tronquées où le temps de calcul est réduit en n'utilisant que des bases plus petites pour les intégrales bi-électroniques à trois et quatre centres. Les différentes bases tronquées employées donnent de bons résultats lorsque l'énergie et les valeurs moyennes de certains opérateurs monoélectroniques sont pris comme critères. Les résultats obtenus pour le moment dipolaire sont moins bons. Si l'on peut prendre les résultats présentés comme guide on peut se demander si l'emploi de grandes bases non tronquées présente un avantage réel vu le prix du calcul.
    Notes: Abstract Some merged basis set calculations are described in which the magnitude of the computational labour is greatly reduced by using smaller Gaussian lobe bases for computing the 3- and 4-centre two-electron integrals, the full basis being employed for all one-electron and one-and two-centre two-electron integrals. The several merged bases that have been investigated have all performed exceedingly well when total energy and some one-electron operator expectation values are used as criteria. The performance with respect to dipole moment is not quite as impressive as for the other expectation values. If present results can be taken as a general guide then it is questionable whether large Gaussian basis calculations that do not make use of the merging procedure have any advantage to offset the greater computing cost involved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00537629
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  • 4
    Electronic Resource
    Electronic Resource
    Trace elements in suspended particulate matter from the Yarra River, Australia (1989)
    Springer
    Hydrobiologia 176-177 (1989), S. 239-251 
    Details
    ISSN: 1573-5117
    Keywords: suspended particulate matter ; phosphorus ; heavy metals ; speciation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Suspended particulate matter (SPM) was collected from two sites in the Yarra River, Australia under a range of flow conditions using a continuous flow centrifuge. The SPM from the upstream, largely rural, site at Warrandyte had higher concentrations of organic matter, phosphorus and manganese. SPM collected from the downstream, largely urban, site at Heidelberg had elevated concentrations of lead and zinc. The concentrations of iron, copper and chromium in the SPM changed little between the two sites. Over the study period, the flow-weighted mean concentration of SPM increased 5-fold between the two sites and the load increased 7-fold. The annual load of SPM transported past Heidelberg was estimated to be 170 000 tonne, with approximately 80% occurring during high flows (〉 15 m3 s-1 ). Detailed study of the SPM concentrations during flood events suggests that the northern tributaries to the Yarra are the main contributors of SPM in the region between Warrandyte and Heidelberg. The mean annual load of total phosphorus transported by the Yarra River at Heidelberg was estimated to be 220 tonne, approximately 2.5 times greater than at Warrandyte. Approximately 60% of this load was associated with SPM. The majority (ca. 80%) of this SPM-bound phosphorus was extractable with 0.1 M NaOH, and is therefore potentially biologically available. There was little difference between the two sites in the flow-weighted mean concentrations of iron, copper and chromium in SPM. The manganese concentration was approximately halved between Warrandyte and Heidelberg, with most of the loss occurring in the exchangeable and reducible fractions. Lead and zinc concentrations in SPM increased 15 to 16-fold between the two sites, with most of this increase occurring in the exchangeable and reducible fractions. This is some cause for concern, since metals in both these fractions could become available to biota under conditions known to exist in the Yarra estuary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026559
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Algal blooms in the Darling-Barwon River, Australia (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 487-496 
    Details
    ISSN: 1573-2932
    Keywords: Cyanobacterial blooms ; Australian rivers ; flow ; stratification ; clay/Fe/P association ; nutrients ; N fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Australian waterbodies have long water residence times, stratification is common, and eutrophication is driven mainly by the internal loads. The 1991 blue-green algal bloom on the Darling-Barwon River was at a time of low river flow (∼100's ML/day) and hot/still conditions. The sustained low flow allowed significant influx of a sulfate-rich saline groundwater and this caused clay flocculation, water clarification and increased photosynthesis in the surface water, and increased sulfate reduction, pyrite formation and Fe mobilisation in anoxic bottom sediments. Since this time similar optimum bloom periods have not produced blooms, or Fe mobilisation, despite high soluble P concentrations. Algal growth during optimum bloom periods is known to be N-limited and it is possible that, in this case, essential trace elements are limiting N-fixation — clay flocculation is a very efficient process of removing trace elements from the water column. Optimum bloom periods can potentially set up a feed-back involving the bottom sediments and increasing sulfate concentration, to resupply surface water with P and trace metals. It is suggested that this operated in late 1991, but not during later optimum bloom periods as no further Fe mobilisation is recorded. The management implication is to maintain sufficient river flow to prevent any significant groundwater influx.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02406888
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    Paper (German National Licenses)
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