Electronic and positron band structures and charge densities of Ga0.5Al0.5N using the empirical pseudopotential method (EPM) are investigated. For the ternary alloy Ga1-xAlxN, the virtual crystal approximation (VCA) is coupled with the pseudopotential method. The energies along Gamma, X and G of Ga1-xAlxN alloy as a function of the mote fraction are calculated. Angular correlation of positron annihilation radiation (ACPAR) along different crystallographic directions in Ga0.5Al0.5N is calculated. Other quantities such as ionicity character and bulk modulus by means of recent models with respect to the mole fraction are discussed. (C) 2004 Elsevier B.V. All rights reserved.