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Positron lifetimes and annihilation lineshape in Cd and au from 4.2 K to the melting points (1977)

Herlach, D. ; Stoll, H. ; Trost, W. ; [weitere]

Springer

Applied physics 12 (1977), S. 59-67

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Details

ISSN: 1432-0630

Schlagwort(e): 61.70 ; 81

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau , Physik

Notizen: Abstract By means of an integrated source-specimen technique the temperature dependence of positron lifetimes and annihilation lineshapes has been measured, on the same specimens of gold and cadmium from 4.2K to the melting points, and also in electronirradiated and quenched gold. The anomalous temperature dependence of positron annihilation at intermediate temperatures (200 to 350 K in Cd, 270 to 750 K in Au) discovered by Lichtenberger, Schulte, and MacKenzie is confirmed. The data are incompatible with the idea that the intermediate temperature dependence is due to thermal expansion. They are well explained by an extension of the trapping model which includes the formation of metastable self-trapped positrons. From lineshape measurements after electron irradiation at 180 K and after quenching it is deduced that the trapping rate of positrons at vacancy-type defects in Au is temperature independent below room temperature.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00900069

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Digitale Medien

Hartree-Fock calculation of cohesive energies and equilibrium lattice constants for solid Li and Be (1975)

Stoll, H. ; Preuss, H.

New York, NY : Wiley-Blackwell

International Journal of Quantum Chemistry 9 (1975), S. 775-787

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Details

ISSN: 0020-7608

Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A method is described for calculating cohesive energies of solids in the single-determinant approximation including the full Hartree-Fock exchange. The method involves (1) the construction of a rapidly convergent series in vectors of the direct and reciprocal lattice for the Fock matrix, (2) a decoupling procedure for the k-dependence of the Fock matrix, which works even in the case of strong interatomic overlap. An application to Li and Be is given. Agreement with experiment to 10% is achieved for the cohesive energies and to 5% for the equilibrium lattice constants.

Zusätzliches Material: 2 Ill.