Positron and electron energy bands and wavefunctions, Fermi surface, density of states, Hall coefficient and positron annihilation in beryllium, using a new technique for Brillouin zone integration

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1978

OSTI ID:6316132

Oriade, J O.O.

The new technique, called BIQ, is an analytic biquadratic scheme. The use of an accurate band structure and this new integration scheme has produced accurate densities of states for Be. For the first time the Fermi energy, E/sub F/, has been found at a positron consistent with the observed hole conductivity in Be. The Hall coefficient has been calculated from our band structure; the value obtained for Be is in excellent agreement with experiment. The calculated Fermi surface of Be also is in excellent agreement with experiment. The calculated angular distribution of annihilation photons, ADAP, and the positron lifetime, tau, were found to depend strongly on the electron and positron charge densities and on the electron group velocities, v/sub n/(k). The calculated angular distribution, ADAP, was found also to depend strongly on the electron Bloch functions, PSI/sub n,k/(r), and on the shape of the Fermi surface. Both the calculated and the experimental ADAP cuves were found to deviate strongly from the free-electron parabola, and the calculated curve was found to bear a reasonable resemblance to the experimental curve. The calculated value for tau/sup -1/ was found to be only about twenty per cent smaller than the experimental value. We conclude from the comparison of our values with experiment that electron-positron correlation reduces the magnitude of band structure effects on ADAP. However, we find that this correlation and other many-body effects produce only a small net enhancement in the overall annihilation rate. This conclusion is contrary to the results of recent many-body calculations for the free electron gas.

• Research Organization: Illinois Univ., Chicago (USA)
• OSTI ID: 6316132
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
ALKALINE EARTH METALS
ANALYTICAL SOLUTION
ANGULAR DISTRIBUTION
ANNIHILATION
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BASIC INTERACTIONS
BERYLLIUM
DATA
DISTRIBUTION
ELECTROMAGNETIC INTERACTIONS
ELECTRONIC STRUCTURE
ELEMENTARY PARTICLES
ELEMENTS
ENERGY LEVELS
FERMI LEVEL
FERMIONS
HALL EFFECT
INFORMATION
INTERACTIONS
LEPTONS
LIFETIME
MANY-BODY PROBLEM
MASSLESS PARTICLES
METALS
NUMERICAL DATA
PHOTONS
POSITRONS
THEORETICAL DATA