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  • Springer  (2)
  • American Institute of Physics (AIP)  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Quantum chemistry without diagonalization: An extension of the Lanczos method to molecules and solids (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 1222-1228 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We implement here the recursion method and its extensions to the case of nonorthogonal bases (Riedinger et al., 1989) for determining the electronic structure of molecules of intermediate size. The recursion method, which is a variant of the Lanczos method, has been introduced by Heine, Haydock, and Kelly in solid state physics during the 1970s. It provides an invaluable tool for studying the electronic structure of solids and amorphs in direct space, without explicit diagonalization, in the case of orthogonal bases. Applications with nonorthogonal bases are made on the decavanadate ion (V10O28)6−, described within the extended Hückel model. Our extension of the recursion method may even be applied to molecules of large size or to infinite systems, where the usual methods of quantum chemistry fail. It applies to crystals as well as to glasses and molecules, for which no translational symmetry exists.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460030
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  • 2
    Electronic Resource
    Electronic Resource
    A short CI expansion for a symmetry-adapted description of localized hole states: Application to the 3dσu hole state of the Cu2 + ion (1982)
    Springer
    Theoretical chemistry accounts 61 (1982), S. 379-385 
    Details
    ISSN: 1432-2234
    Keywords: Configuration interaction ; Localized hole states ; Cu2 + ion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A simple formalism is developed to describe by means of a symmetry-adapted wavefunction the localized hole states which may arise in symmetric systems. A short CI expansion is generated in a systematic way from the delocalized molecular orbitals of the SCF ground state. For the 3dσu hole state of the Cu2 + ion, the symmetry adapted and the broken symmetry solutions approximately correspond to the same energy at that level of CI.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00550416
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  • 3
    Electronic Resource
    Electronic Resource
    The ground state of MoCr(O2CH)4 at theab initio SCF and CI levels. A symmetry adapted RHF energy functional with an artificial double minimum (1984)
    Springer
    Theoretical chemistry accounts 66 (1984), S. 65-75 
    Details
    ISSN: 1432-2234
    Keywords: MoCr(O2CH)4 ; ab initio SCF, CI ; energy functional ; double minimum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ab initio restricted Hartree-Fock (RHF) calculations carried out on the ground state of MoCr(O2CH)4 lead to two distinct energy minima according to the initial guess made for the set of trial vectors. It is shown that these two symmetry-adapted wavefunctions can be correlated with a twofold degenerate broken-symmetry solution previously characterized for the related system of higher symmetry Cr2(O2CH)4. Complete CI expansions have been carried out from either RHF polarized wavefunction using as a basis the set of eight frontier MO's with high metal character. These expansions yield poorly resymmetrized wavefunctions. A similar CI expansion has finally been carried out from a wavefunction resymmetrized at the SCF level and corresponding to a saddle point of the RHF energy hypersurface. The total energy associated with this latter expansion is the lowest obtained in the present work. The natural orbital analysis corresponds to (σ)1.86(π)3.58(δ)1.54(δ)0.46(π)0.42 (δ*)0.14 and shows that this resymmetrized CI expansion is in many respects similar to the correlated wavefunctions obtained for the homobinuclear parent systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00577140
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