Calculation Of Positron Annihilation Rates In Metals Using Different Enhancement Factors

Abstract

Positron annihilation rates in metals were calculated using the enhancement factors of Boronski and Nieminen (1986), Sterne and Kaiser (1991), and the local density approximation by solving the Kohn-Sham type of equation self-consistently for electron-positron densities in metals using an interactive scheme. The experimental and calculated positron annihilation rates in metals exhibit the same trend. The results obtained revealed that there is no significant difference in the positron annihilation rates calculated using the enhancement factors of Boronski and Nieminen (1986) and that of Sterne and Kaiser (1991). Furthermore, the results revealed that the positron annihilation rates calculated using the enhancement factor of the local density approximation were in better agreement with experimental values than the ones calculated using the enhancement factors of the two other models or approximations. This shows that the use of local density approximation is better in the prediction of positron annihilation rates in metals; and that the enhancement factor of the local density approximation explains electron-positron correlation in metals better than other models or approximations. Explanations for the observed discrepancies between the experimental and calculated positron annihilation rates in metals are given.

Keywords: Metals, positrons, annihilation rates, enhancement factors

Nigerian Journal of Physics Vol. 19 (1) 2007: pp. 1-8