Pressure Dependence of Positron Annihilation in Si

The pressure dependence of the electron‐positron and the electron‐electron momentum densities in silicon are studied. The observations that the electron‐positron momentum density increases more rapidly with pressure than the electron‐electron momentum density alone is explained in terms of increased positron penetration into the ion cores. The computational technique used here is based on the independent‐particle model (IPM) coupled with the use of the electron pseudo‐wave functions.