Theoretical studies of positron annihilation in GaP1-xNx

Angular correlation of positron annihilation radiation (ACPAR) along differ ent crystallographic directions in GaP1-xNx is calculated. It is observed t hat the electron-positron momentum density increases rapidly with increasin g nitrogen content. The computational technique used here is based on the i ndependent-particle model (IPM) coupled with the use of the electron pseudo -wave function and the virtual crystal approximation (VCA) which incorporat es compositional disorder as an effective potential. The variation of the p ositron lifetime in these alloys is also presented.