Ab initio phonon dispersion calculations for TixGanAsm and TixGanPm compounds

We have calculated and predicted the phonon dispersion and phonon density of states of GanAsmTi and GanPmTi half-metallic semiconductor compounds using an eight-atom simple cubic cell structure. We use the ab initio density functional frozen phonon method in the LDA and GGA approximation. We have first determined the phonon spectra of GaAs and GaP and found very good agreement with experimental results. We find that (i) in all GanAsmTi and GanPmTi cases studied, the acoustic modes could be easily identified with the phonon modes of GaAs and GaP respectively, and (ii) additional Ti high frequency optical modes appear well separated in all the Brillouin zone for Ga3As4Ti and Ga3P4Ti semiconductor compounds.