Angular Correlation of Positron Annihilation Radiation in Chromium and Molybdenum

Angular correlation of positron annihilation radiation in Cr and Mo were measured. Self-consistent band structure calculations for Mo were carried out by the APW method with state-dependent potentials. Theoretical angular correlations for Cr and Mo were also calculated by the APW method. Observed fine structures on the angular correlations and the crystalline anisotropies were well reproduced by the calculations. However, when the theoretical and experimental correlation curves were normalized to an equal area, the theoretical curves were consistently lower in counting rate than the experimental ones in small angle region, and higher in large angle region. This type of discrepancy between the theory and the experiment is the same as we previously found in V and Nb, and is ascribed to the electron-positron correlation effects.