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  • 24.10.Cn  (3)
  • Extended Hückel calculations
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 342 (1992), S. 161-167 
    ISSN: 1434-601X
    Keywords: 24.10.Cn ; 25.70.−z
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present a coupled set of equations for the one-body density matrix and the two-body correlation function consistent with trace relations and conservation laws which provide an extension of correlation dynamics on the two-body level. The additional interaction terms are discussed in the context of time-dependent G-matrix theory and NQCD and studied numerically by one-dimensional calculations for colliding finite fermion systems.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 331 (1988), S. 43-51 
    ISSN: 1434-601X
    Keywords: 24.10.Cn ; 24.60 ; 25.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We show how the fluctuating part of the residual coupling between collective and intrinsic motion of a dissipative heavy-ion collision induces correlations in either subspace. They lead in general to a transport equation for the collective motion, and to a new term in the equation for the one-body density which describes collisions with the collective fluctuations. The resulting redistribution of the single-particle occupation numbers ρα and the evolution of the fluctuations are coupled with each other due to the dependence of the transition rates in the master equation on the fluctuations, and of the transport coefficients on ρα. Considering the special case of a long contact phase, we find the fluctuations to be most effective, with respect to a randomization of ρα, within a certain critical region where they pass from stable to unstable behaviour. Estimates are made for the corresponding relaxation times employing a schematic model.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 337 (1990), S. 175-183 
    ISSN: 1434-601X
    Keywords: 24.10.Cn ; 25.70.−z
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The dynamical description of strongly interacting finite Fermi systems is based on coupled equations of motion for the one-body density matrixρ(11′) and the two-body correlation functionc 2(12, 1′2′) as obtained from the density-matrix hierarchy. The truncation schemes considered exceed the conventional Brueckner-Hartree-Fock scheme and also apply for nonstationary problems. In the limit of slow processes in time the equation of motion for the two-body correlation functionc 2 can be integrated in time and closed expressions can be given for the dynamical evolution ofρ(11′). When performing a Wigner transformation and adopting semiclassical limits this gives a transport equation of the Uehling-Uhlenbeck type for the one-body phase-space distributionf(x,p;t). Furthermore, in the small amplitude limit, we obtain a set of coupled equations for particle-hole (p-h),2p-2p, 2h-2h, 2p-2h, 1p-3h, 1h-3p amplitudes beyond the level of second RPA which provide a genuine basis for the description of giant resonances and their damping width.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 1992-1997 
    ISSN: 0044-2313
    Keywords: Copper antimony sulfide ; sulfo salts ; crystal structure ; phase transitions ; Extended Hückel calculations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cu3SbS3: Crystal Structure and PolymorphismThe hitherto unknown crystal structure of β-Cu3SbS3 at room temperature could be determined from a twinned crystal. The compound crystallizes in the monoclinic system, space group P21/c (No. 14), with a = 7.808(1), b = 10.233(2) and c = 13.268(2) Å, β = 90.31(1)°, V = 1 060.1(2) Å3, Z = 8. An Extended-Hückel-Calculation shows weak bonding interactions between copper atoms which are coordinated trigonal planar. At -9°C a first order phase transition occurs and the crystals disintegrate. The low-temperature modification (γ) crystallizes in the orthorhombic system with a = 7.884(2), b = 10.219(2) and c = 6.623(2) Å, V = 533.6(2) Å3 (-100°C). At 121°C a phase transition of higher order is observed. The high-temperature polymorph (α) of Cu3SbS3 is orthorhombic again. From high-temperature precession photographs the space groups Pnma (No. 62) or Pna21 (No. 33) can be derived. The lattice constants at 200°C are a = 7.828(3), b = 10.276(4) and c = 6.604(3) Å, V = 531.2(2) Å3.
    Notes: Die bisher unbekannte Kristallstruktur von β-Cu3SbS3 bei Zimmertemperatur wurde anhand eines verzwillingten Kristalls ermittelt. Die Verbindung kristallisiert monoklin, RG P21/c (Nr. 14) mit a = 7,808(1), b = 10,233(2) und c = 13,268(2) Å, β = 90,31(1)°, V = 1 060,1(2) Å3, Z = 8. Eine Extended-Hückel-Rechnung ergibt schwach bindende Wechselwirkungen zwischen den trigonal-planar koordinierten Kupferatomen. Bei -9°C erfolgt eine reversible Phasenumwandlung 1. Ordnung, bei der die Kristalle zerfallen. Die Tieftemperaturmodifikation (γ) kristallisiert orthorhombisch mit a = 7,884(2), b = 10,219(2) und c = 6,623(2) Å, V = 533,6(2) Å3 (-100°C). Beim Aufheizen beobachtet man bei 121°C eine Phasenumwandlung höherer Ordnung. Die Hochtemperaturmodifikation (α) von Cu3SbS3 kristallisiert ebenfalls orthorhombisch. Aus Hochtemperatur-Präzessionsaufnahmen ergibt sich Pnma (Nr. 62) oder Pna21 (Nr. 33) als mögliche Raumgruppe. Die Gitterkonstanten bei 200°C sind nach Guinier-Aufnahmen a = 7,828(3), b = 10,276(4) und c = 6,604(3) Å, V = 531,2(2) Å3.
    Additional Material: 3 Ill.
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