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1999 (1)
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1993 (2)
1Author    F. F. Seelig, G. A. BeckerRequires cookie*
 Title    Correlated Atomic Pair Functions by the -Method. I. Ground State 1 J S and Lowest Excited States « J S (n > 1) and TI 3 S of Helium  
 Abstract    Some low n 1 S and n 3 S states of the helium atom are computed with the aid of the e~ e method which formulates the electronic wave function of the 2 electrons as = e~ e F, where q = Z(r\ + r 2) -\r\ 2 and here Z = 2. Both the differential and the integral equation for F contain a pseudopotential V instead of the true potential V that contrary to V is finite. For the ground state, F = 1 yields nearly the Hartree-Fock SCF accuracy, whereas a multinomial expansion in n, r 2 , r\ 2 yields a relative error of about 10 -7 . All integrals can be computed analytically and are derived from one single "parent" integral. 
  Reference    Z. Naturforsch. 54a, 711—717 (1999); received October 29 1999 
  Published    1999 
  Keywords    Electron Correlation, Pair Function, 5-states of Helium 
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 TEI-XML for    default:Reihe_A/54/ZNA-1999-54a-0711.pdf 
 Identifier    ZNA-1999-54a-0711 
 Volume    54 
2Author    B. Joulakian, C. DalRequires cookie*
 Title    The Effect of Correlation on the Double Ionization of Helium by Fast Electrons  
 Abstract    The double ionization of helium by fast electrons is studied by using a correlated double con-tinuum wave function describing the two ejected electrons. 
  Reference    Z. Naturforsch. 48a, 255—256 (1993); received October 17 1991 
  Published    1993 
  Keywords    Double-ionisation processes, Scattering cross-section, Electron scattering, inelastic, Electron correlation 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0255.pdf 
 Identifier    ZNA-1993-48a-0255 
 Volume    48 
3Author    Michal Jaszuński, Antonio RizzoRequires cookie*
 Title    Ab initio Study of Nitrogen-14 Nuclear Quadrupole Coupling and NMR Signal Linewidths in Some Azoles  
 Abstract    Ab initio values of Nitrogen l4 N Nuclear Quadrupole Coupling Constants (NQCC's) are calcu-lated for a series of methyl-substituted azoles in the Multiconfigurational SCF (MCSCF) approx-imation. The four triazoles and two tetrazoles studied here are all isoelectronic. This enabled us to use the same level of approximation -basis set and active space -for all the molecules. The computed NQCC's are used to estimate the relative widths of the U N NMR signals, assuming an identical effect of molecular tumbling for all the nuclei in a molecule and neglecting solvent effects. The linewidths for the unsubstituted N atoms are, in agreement with experiment, much larger than for the methyl-substituted N atom. For the 1-methyl-tetrazole we present also the NMR shielding and spin-spin coupling constants and discuss in some more detail the dependence of all calculated NMR properties on the basis set and correlation effects. 
  Reference    Z. Naturforsch. 53a, 362—369 (1998); received December 31 1997 
  Published    1998 
  Keywords    14 N NQCC, Azoles, MCSCF, Ab initio, Electron Correlation 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0362.pdf 
 Identifier    ZNA-1998-53a-0362 
 Volume    53 
4Author    M. V. Eremin, R. Markendorf, S. G. SolovjanovRequires cookie*
 Title      
 Abstract    The energy dispersion of the chain band has been determined in the framework of the Hubbard model. The results are in agreement along the T-S and T -Y lines of the Brillouin zone with photoemission data. The amount of d 3z2_r2 states is zero at y = 0 and increases to 10% at y = 1. The admixture is due to the hybridization of C u (l) dy2_z2 states with Cu(2) d 322_P2 states via apical oxygen. The effect of this admixture on the N Q R frequency of Cu(2) is discussed. 
  Reference    Z. Naturforsch. 49a, 379—384 (1994); received September 7 1993 
  Published    1994 
  Keywords    N Q R, Electron correlation, Chain band, d 3z2_r2 states, Band dispersion 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0379.pdf 
 Identifier    ZNA-1994-49a-0379 
 Volume    49 
5Author    KennethE. Edgecombe, VedeneH. Smith, Florian Müller-PlatheRequires cookie*
 Title    Nonnuclear Maxima in the Charge Density  
 Abstract    Basis-set and electron-correlation effects on the appearance and disappearance of nonnuclear maxima in the electron density are examined in Li 2 , Na 2 , Na 4 and Na 5 . It is shown that nonnuclear attractors can be removed in all cases except Li 2 . The appearance of a pseudoatom in a lithium molecule correlates remarkably well with the size of the region, in an atomic calculation, of V 2 Q (r) for the valence shell of the atom. This and the fact that the pseudoatom is also present in the promolecule indicate that the pseudoatoms are remnants of, or in fact are portions of, atoms that are not perturbed enough in the molecule to remove an essentially atomic characteristic. 
  Reference    Z. Naturforsch. 48a, 127—133 (1993); received May 27 1992 
  Published    1993 
  Keywords    Li 2, Na 2, Topological analysis, Pseudoatoms, Charge density, Electron correlation 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0127.pdf 
 Identifier    ZNA-1993-48a-0127 
 Volume    48