Enhancement factors for positron annihilation studies
Abstract
Electron and positron densities for a number of positron binding atoms and ions are used to benchmark methods used to compute positron annihilation rates in solids. The electron and positron densities from ab initio calculations are multiplied by some commonly used enhancement factors and integrated to give the annihilation rate. These are then compared with the close to exact annihilation rate calculation using the fully correlated positronic atom wave functions. The results reveal deficiencies in the onecomponent localdensity approximation (LDA) and the BoronskiNieminen twocomponent LDA. A simple modification of the onecomponent LDA leads to an enhancement factor that predicts annihilation rates more reliably for some positronic systems with a minimal increase in complexity. An approach based on an existing version of the generalized gradient approximation tends to underestimate the annihilation rate with the valence electrons.
 Publication:

Physical Review B
 Pub Date:
 June 2002
 DOI:
 10.1103/PhysRevB.65.235103
 Bibcode:
 2002PhRvB..65w5103M
 Keywords:

 78.70.Bj;
 71.60.+z;
 71.15.Mb;
 36.10.k;
 Positron annihilation;
 Positron states;
 Density functional theory local density approximation gradient and other corrections;
 Exotic atoms and molecules