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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 96 (1974), S. 3328-3330 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 95 (1973), S. 6133-6134 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 95 (1973), S. 7889-7891 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 97 (1975), S. 6268-6270 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 6668-6686 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An interdimensional degeneracy linking the orbital angular momentum projection ||m|| and spatial dimension D gives D-dimensional eigenstates for H+2 by simple correspondence with suitably scaled D=3 excited states. The wave equation for fixed nuclei is separable in D-dimensional spheroidal coordinates, giving generalized two-center differential equations with parametric dependence on the internuclear distance R. By incorporating||m|| into D, the resulting eigenstates can be classified by the two dimension-independent "radial'' quantum numbers denoted in united atom notation by k and l−||m||, corresponding, respectively, to the number of ellipsoidal and hyperboloidal nodal surfaces in the wave function. The two eigenparameters, the energy ED(R), and a separation constant AD(R) related to the total orbital angular momentum and the Runge–Lenz vector, have been determined numerically for the ground state and several low lying excited states for selected dimensions from D=2 to D=100.The system simplifies greatly in the limit D→∞, where the electronic structure reduces to a classical electrostatic form with the electrons in a fixed geometrical configuration relative to the nuclei, akin to the traditional Lewis electron-dot structure. For a given R, the energy E∞ reduces to the minimum of an effective potential surface and the separation constant A∞ reduces to a simple function of the energy. The surfaces are separable in spheroidal coordinates resulting in analytical expressions for the energy in terms of the coordinates. The surfaces exhibit a characteristic symmetry breaking as functions of R, changing from a single minimum surface in the united atom limit (R→0) to a double minimum surface in the separated atom limit (R→∞). Effects of this symmetry breaking are found at finite D as well. Analysis of excited state D-dimensional energies reveals that bonding in H+2 is determined primarily by k, contrary to the standard scheme of bonding and antibonding molecular orbitals, which in the case of H+2 correspond to even and odd l−||m||, respectively. When the D-dimensional energies are examined as functions of 1/D, the resulting curves resemble typical perturbation diagrams with 1/D as the perturbation parameter.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 4997-5008 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Correlation energies (CEs) for two-electron atom ground states have recently been obtained to good approximation from a simple perturbation treatment using 1/D as the expansion parameter, with D the dimensionality of space. In hydrogenic units, the CE varies almost linearly with 1/D between limits at D→1 and D→∞ which are exactly calculable. However, for D→∞ the CE is only about 35% smaller than the "true-world'' value at D=3. This is in striking contrast to the analogous error in the mean field approximation of statistical mechanics, which vanishes for sufficiently large D. Here we show that the CE for D→∞ can be made to vanish by modifying the Hartree–Fock (HF) variational wave function. A separable form is retained but a factor aitch-theta(θ) is included, with θ the angle between the electron–nucleus radii r1 and r2. Likewise, the error in the HF value for the first derivative of the energy with respect to 1/D can be made to vanish by employing a suitable choice of coordinates in separate factors of the wave function. The choice is determined by the vibrational normal modes of the electrons about the rigid configuration attained in the D→∞ limit. We estimate that these improvements in the HF wave function at large D will reduce the CE for D=3 by about a factor of 10 or more for any two-electron atom. We also relate our results to those obtained with hyperspherical coordinates and show that the large-D limit accounts for the success enjoyed by the hyperspherical approximation at D=3. These findings offer prospects for reducing CEs for multielectron systems by exploiting dimensional calibration of the HF wave function.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7791-7796 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The scaling of the Schrödinger equation with spatial dimension D is studied by an algebraic approach. For any spherically symmetric potential, the Hamiltonian is invariant under such scaling to order 1/D2. For the special family of potentials that are homogeneous functions of the radial coordinate, the scaling invariance is exact to all orders in 1/D. Explicit algebraic expressions are derived for the operators which shift D up or down. These ladder operators form an SU(1,1) algebra. The spectrum generating algebra to order 1/D2 corresponds to harmonic motion. In the D→∞ limit the ladder operators commute and yield a classical-like continuous energy spectrum. The relation of supersymmetry and D scaling is also illustrated by deriving an analytic solution for the Hooke's law model of a two-electron atom, subject to a constraint linking the harmonic frequency to the nuclear charge and the dimension.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 433-442 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: If the Hamiltonian of a two-electron atom is generalized in a natural way to arbitrary spatial dimension D, an especially simple case is found in the D=1 limit. While the ground state energy is singular at this point, a scaling argument reduces the problem to a limiting Hamiltonian with only two degrees of freedom in which the Coulombic potentials all reduce to δ functions. Since the singularity at D=1 dominates the energy at nearby dimensions, this limit forms the basis for an expansion in (D−1)/D which is reasonably accurate at D=3. By combining results from this expansion with the 1/D expansion about the D→∞ limit, estimates of the energy at D=3 are obtained with accuracy orders of magnitude better than that of either series alone. The simplicity of the D=1 and large-D limits and the accuracy of this method allow some qualitative insight into the physical features contributing to correlation effects in small atoms. Analysis of other singularities suggests that the 1/D series has zero radius of convergence for two-electron atoms. We conclude with a discussion of excited states and larger atoms and make some appealing connections with the orbital picture.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 4557-4562 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Recently developed approximation methods for quantum mechanical problems which treat the spatial dimension D as an expansion parameter offer approximations to energy levels at arbitrary D. Rather than simply being a detour to the D=3 case, there is physical interest in nonphysical values of D due to degeneracies between states in different dimensions. For example, such degeneracies make it possible to calculate some excited states of two-electron atoms in three dimensions from the ground state energy at nonphysical values of D. Such relationships can be exploited in a simple derivation of the hydrogen atom spectrum in arbitrary D, using only the solution at D=1 and a combination of inter- and intradimensional symmetry arguments. Applications to the Yukawa potential and an anharmonic oscillator are also presented. A large class of interdimensional degeneracies is found for two-electron atoms. Approximate degeneracies are also identified for these atoms which allow highly excited D=3 states to be treated as perturbed low-lying states in another dimension. The approximate degeneracies also serve to generalize the treatment of the hydrogen atom spectrum in a way appropriate to two-electron atoms.
    Type of Medium: Electronic Resource
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