The influence of the lattice relaxation on the optical properties of GaNxAs1−x alloys

► Novel gain materials based on III-N-V compounds were investigated. ► Optical properties of GaNxAs1−x with and without lattice relaxation were calculated. ► 'Special quasirandom structures' (SQS) approach of Zunger to reproduce was used. ► For relaxed alloys, the lattice constants vary linearly as function of composition x. ► If internal relaxation is not allowed, significant deviations from Vegard's law occur.