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  • 11
    Electronic Resource
    Electronic Resource
    Ab initio CI study of chemical reactions of singlet and triplet imidogen (NH) radicals (1983)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 105 (1983), S. 5547-5557 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00355a004
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  • 12
    Electronic Resource
    Electronic Resource
    Ab initio MRD CI investigation of the optical spectra of C4 and C5 clusters (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 1066-1073 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ground and excited electronic states of linear and rhombic C4 and linear C5 clusters have been studied with ab initio single reference and multireference configuration interaction calculations. The spectrum of linear C4 is characterized by the existence of low-lying Π states at 1–1.5 eV above the 3Σ−g ground state. In rhombic C4, which has very similar ground state energy as the linear form, the first allowed transition is found at 2.4 eV. The optical spectrum of linear C5 exhibits some similarities with that of linear C3: in both molecules the ground state is 1Σ+g and the lowest allowed transition, 1Πu←1Σ+g, is about 3 eV above the ground state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454276
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  • 13
    Electronic Resource
    Electronic Resource
    Alternancy symmetry: A unified viewpoint (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 1722-1735 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A general formulation of the alternancy symmetry adaptation for the semiempirical Pariser–Parr–Pople (PPP) type Hamiltonians is presented at both the spin-orbital and spin-adapted many-electron levels. The derivation of the general form of the alternancy symmetry conjugation operators is based solely on the tight-binding approximation for the short range one-particle part of the Hamiltonian considered. It starts by a simple formulation of the desired invariance properties of the PPP type Hamiltonian. Using algebraic properties of the unitary group generators and of their particle number nonconserving extensions, it leads to a completely explicit and general form for the alternancy symmetry conjugation operators. In this way the prior descriptions, which become special cases of this general formulation, are interrelated and unified. The spin and quasispin character of certain components of these operators are also pointed out and explicitly derived. The spin-adapted version is based on the unitary group formulation of the valence bond-type approach. A completely general formulation is given which applies to many-electron states of an arbitrary multiplicity of neutral systems, either of the normal kind with an identical number of starred and nonstarred sites, or of the radicaloid character with different numbers of starred and nonstarred sites. An explicit form of the dependence of the relative phase factor of the alternancy symmetry conjugation operator on the total spin, total electron number and on the number of starred and nonstarred sites is also given. General rules for the construction of spin and alternancy symmetry-adapted states are illustrated on a few simple examples. Finally, a brief discussion of the implications of the alternancy symmetry is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449359
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  • 14
    Electronic Resource
    Electronic Resource
    Silicon and germanium clusters. A theoretical study of their electronic structures and properties (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 3301-3310 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Silicon and germanium clusters containing three to seven atoms have been studied with the pseudopotential MO-LCAO method followed by configuration interaction procedure. Si and Ge clusters have very similar electronic structures and consequently analogous physico-chemical properties but differ substantially from small carbon clusters. Linear structures are clearly less favorable than more compact structures. On the other hand, some planar geometries possess considerable stability. The Si and Ge clusters which are sections of the diamond-type crystal lattice are less stable than clusters which can be considered as segments of closed-packed lattices or as steps in pentagonal crystal growth. The reason is that the majority of atoms in small clusters are surface atoms which cannot assume the tetrahedral coordination characteristic of Si and Ge bulk atoms. The appearance of typical bulk properties is expected only for very large Si and Ge clusters with small surface atoms/bulk atoms ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450262
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  • 15
    Electronic Resource
    Electronic Resource
    Methods of Calculation of Polarographic Currents for Depolarization Schemes involving Reactions of Higher Order (1954)
    [s.l.] : Nature Publishing Group
    Nature 174 (1954), S. 233-234 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] If the depolarization process at the dropping mercury electrode involves a reaction of the second or higher order, the depolarization current resulting from the flux of the depolarizer at the electrode surface can be calculated by solving the following general system of equations : da, dsa; 2x ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/174233a0
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  • 16
    Electronic Resource
    Electronic Resource
    ПРИМЕНЕНИЕ МЕТОДА СА МОСОГЛАСОВАННОГО ПО ЛЯ К ТЕОРИИ ПОВЕРХНОСТН ЫХ СОСТОЯНИЙ ЭЛЕКТРО НОВ В КРИСТАЛЛЕ (1958)
    Springer
    Czechoslovak journal of physics 8 (1958), S. 153-153 
    Details
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01603681
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  • 17
    Electronic Resource
    Electronic Resource
    Application of the self-consistent field method to the theory of surface states of electrons in a crystal (1958)
    Springer
    Czechoslovak journal of physics 8 (1958), S. 148-152 
    Details
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is shown under what conditions there exist solutions to the Hartree-Fock equation, which are localized in the neighbourhood of the surface of the crystal. The results obtained earlier as to the number and character of the localized solutions of the single electron Schrödinger equation of electrons in a limited crystal, can be applied to the localized solutions of the Hartree-Fock equation after accepting plausible assumptions. A linear combination, having analogical properties to the Wannier function, can be formed from the solution of the Hartree-Fock equation for an infinite crystal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01603680
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  • 18
    Electronic Resource
    Electronic Resource
    Aproximate pairing properties of SCF solutions in highly symmetric heteroatomic systems (1967)
    Springer
    Theoretical chemistry accounts 8 (1967), S. 244-248 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es werden genäherte alternierende Eigenschaften für Hartree-Fock-Lösungen hochsymmetrischer heterocyclischer Moleküle abgeleitet. Diese Moleküle haben eine alternierende Topologie, sie sind aus zwei Sorten von Atomen in solcher Weise aufgebaut, daß die Atome der ersten Sorte in die Atome der zweiten Sorte — und umgekehrt — transformiert werden können.
    Abstract: Résumé Des propriétés d'accouplement orbital approché sont prouvées pour les solutions de type Hartree-Fock des molécules hétéroatomiques hautement symétriques. Ces molécules ont une topologie alternante et sont formées de deux classes d'atomes de telle sorte qu'il existe une opération interchangeant les atomes des deux classes.
    Notes: Abstract Approximate pairing properties are proved for the Hartree-Fock solutions for highly symmetric heteroatomic molecules. These molecules have an alternant topology and are built from two kinds of atoms in such a way that by an operation the atoms of one kind go over into the atoms of the second kind and vice versa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00527310
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  • 19
    Electronic Resource
    Electronic Resource
    General properties of the Hartree-Fock problem demonstrated on the frontier orbital model (1975)
    Springer
    Theoretical chemistry accounts 36 (1975), S. 149-161 
    Details
    ISSN: 1432-2234
    Keywords: Hartree-Fock-problem ; Frontier molecular orbital model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The general Hartree-Fock energy in the frontier orbital model in the terms of independent variables is given. The existence conditions for extrema of this expression are derived and their relation with various types of solutions of the HF problem as RHF, UHF and complex wavefunctions is shown. The connection between overall properties of the energy surface and the local properties i.e. the stability and instability conditions of various kinds is demonstrated. The conditions for the occurrence of “strange” HF solutions are expressed in terms of quantities characterizing the correlation effects. This shows explicitly that the lack of respecting the electronic correlation is the reason for the occurrence of the “strange” HF solutions for the molecular configurations which exhibit a certain amount of diradical character.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00572556
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  • 20
    Electronic Resource
    Electronic Resource
    A note on the parameters for heteroatoms in Pariser-Parr-Pople (PPP) calculations (1970)
    Springer
    Theoretical chemistry accounts 19 (1970), S. 92-97 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Results of a parameter study of aromatic amines by the standard Pariser-Parr-Pople method are briefly reported. An analysis of the many-electron Hamiltonian of the PPP model provides insight into the relative importance of the one-center parameters in the cases of atoms contributing two, one, and no π-electrons. Results for 9-borafluorene provide an additional illustration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00527381
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