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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 22 (1982), S. 115-125 
    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: We have investigated the conformational dependences of the torsional potential and dipole moment of double-rotor molecules related to acetone, using semiempirical and ab initio calculations and expressing the results in terms of limited Fourier-series expansions. The use of the isodynamic operations of nonrigid molecules to obtain symmetry-adapted quasianalytic forms for the various properties helps compute the representative surfaces with a minimum number of points. Potential surfaces have been calculated for planar ground-state acetone (CNDO/2, STO/3G, and STO/4-31G) and both pyramidal excited-triplet acetone and ground-state dimethylamine (CNDO/2). For groundstate acetone STO/4-31G brings the results obtained with STO/3G closer to those from CNDO/2 and from experiment. The potential surface of excited-triplet acetone appears intermediate between those of ground-state acetone and dimethylamine. For dipole moments the convergence of the harmonic expansions of the vector components is slower than that of the torsional potential whereas that of the vector magnitude is faster.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 65 (1997), S. 241-256 
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A rigorous approach of density functional theory (DFT) for open-shell multifermionic systems is devised, using a local-scaling transformation (LST) scheme involving a single scalar function f(r). Within the orbit θN induced by a model wave function (MWF) _Ψ, the total energy of space or spin degenerate or nondegenerate states is expressed as an exact functional of the single-particle density ρ(r). In the first step, it is shown how the reduced density functions and matrices (RD Fs and Ms) of any order (s=1,…,N-1) of an (open or closed) N-fermion system can be expressed as functionals of the one-fermion charge density. The spatial components (which depend on the spin configuration of the fermions) of the RD Fs and Ms of orders 1 and 2, and the resulting charge and spin distribution and correlation densities, are functionals of the one-fermion charge density. We form the manifolds of the charge and spin distribution and correlation energy functionals, from which the theory can be extended to degenerate states of a spinless Hamiltonian. For multielectronic systems, the spin densities and spin-pair correlations as well as the spin-orbit and spin-spin interactions are determined by the function ρ(r). In the second step, it is shown how the expectation values of s-particle operators, in particular those of spin-including mono- and biparticle operators, are functionals of the monoparticle density ρ(r). We give general expressions for the expectation values of spin-free, spin-field, spin-orbit and spin-spin interaction operators in degenerate states. We show how to express the energy functional of the spin manifolds of a system described by a Schrödinger Hamiltonian. The use of an LST, which preserves spin symmetry, to build this functional must fulfill certain conditions in order to maintain the space symmetry of the system. We investigate the dependence of the Weizsaecker and extended Thomas-Fermi kinetic energy terms and of the Coulomb attraction, repulsion, and exchange potential energy terms on the choice of the MWF, i.e., on the induced orbit and on the spin configuration of the system.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 241-256, 1997
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  • 3
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Following the previous article (Part I), we express the total nonrelativistic energy for spin manifolds of open-shell multielectronic systems, within an orbit θN induced by a model wave function (MWF) _Ψ using a single local-scaling transformation (LST) as an exact functional of the single-particle density ρ(r) or, alternatively, of the LST scalar function f(r). We derive the corresponding Euler-Lagrange variational equations: one implicit in ρ(r), which can be solved iteratively through steps involving f(r), and one explicit in f(r), derived from the total energy as a functional of f(r). Both equations fulfill the space and spin symmetries characterizing the system. The problems arising from the specificities of these two highly nonlinear integrodifferential equations are discussed. The optimal charge density ρ(r) derived from these equations is N- and v-representable and determines the optimal spin density σ(r) as well. Accurate optimal values of all observables can be derived from this scheme using standard procedures.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 257-268, 1997
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  • 4
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 68 (1998), S. 75-75 
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Type of Medium: Electronic Resource
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