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  • 1990-1994  (3)
  • 1975-1979
  • 1840-1849
  • 1991  (3)
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  • 1990-1994  (3)
  • 1975-1979
  • 1840-1849
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Pseudopotential approaches to Ca, Sr, and Ba hydrides. Why are some alkaline earth MX2 compounds bent? (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 1360-1366 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quasirelativistic and nonrelativistic 10-valence-electron pseudopotentials for Ca, Sr, and Ba are presented. Results of calculations with 6s6p5d basis sets for MH, MH+, and MH2 are compared with all-electron and 2-valence-electron pseudopotential calculations with and without core-polarization potentials. The 10-valence-electron pseudopotential approach agrees well with all-electron calculations. It circumvents problems for the 2-valence-electron pseudopotentials arising from an incomplete separation of valence and subvalence shells in polar molecular systems due to strongly contracted occupied (n−1)-d orbitals. All higher-level calculations show SrH2 and BaH2 to be bent with angles of ∼140° and 120°, respectively, while CaH2 is linear with a flat potential-energy surface for the bending motion. The use of a core-polarization potential together with the 2-valence-electron pseudopotential approach allows an investigation of the relative importance of core-polarization vs direct d-orbital bonding participation as reasons for the bent structures. The calculations strongly suggest that both contribute to the bending in SrH2 and BaH2. Even at the Hartree–Fock level of theory 10-valence-electron pseudopotential calculations given reasonable angles when the potential-energy surface is not exceedingly flat, and only moderately contracted basis sets including both compact d functions and diffuse p functions are used. The effect of core-valence correlation and the importance of f functions also are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459993
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Limits for two-photon ande + e − decay widths of positron-electron scattering resonances for√s=1.78 to 1.92 MeV (1991)
    Springer
    The European physical journal 340 (1991), S. 209-218 
    Details
    ISSN: 1434-601X
    Keywords: 14.80.Pb ; 13.10. + q ; 12.20.Fv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Motivated by the observation of energy- and momentum-correlatede + e − pairs in heavy ion collisions, a search for resonances ine + e − scattering at the corresponding energies has been made. Thee + e − decay channel is analyzed in a time window from ∼ 10−13 s to ∼ 10−11 s with a set-up optimized for low-background detection of delayede + e − decays. The two-photon decay channel of a hypothetical resonance is investigated by measuring the two-photon annihilation-in-flight excitation function. New upper limits for the partiale + e − decay width Γee of a few meV are derived for total centre-of-mass energies √s between 1.78 and 1.92 MeV, taking into account the dilepton as well as the two-photon decay of a neutral resonance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01303834
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Energy-adjustedab initio pseudopotentials for the second and third row transition elements: Molecular test for M2 (M=Ag, Au) and MH (M=Ru, Os) (1991)
    Springer
    Theoretical chemistry accounts 78 (1991), S. 247-266 
    Details
    ISSN: 1432-2234
    Keywords: Pseudopotentials ; Transition metals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Recently published nonrelativistic and quasirelativistic energy-adjustedab initio pseudopotentials representing the M(Z−28)+ cores of the second row transition metal atoms and the M(Z−60)+ cores of the third row transition metal atoms have been tested in SCF, CI(SD) and CEPA1 calculations of the spectroscopic constants (R e ,D e , and ω e ) of the ground states of the neutral and singly charged silver and gold dimers, and in state averaged CASSCF and multi-reference CI(SD) calculations of the spectroscopic constants (R e ,D e , ω e , μ e , ∂μ/∂R). Comparison is made with experimental and reliable theoretical data where available; in the case of the hydrides, additional calculations with pseudopotentials published by other groups have been made for comparison.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01112848
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    Paper (German National Licenses)
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