In this work, we have calculated ab initio the phonon dynamics of the Ga-rich GaAs (100) (1 × 1), GaAs (100) (2 × 1), GaN (100) (1 × 1), GaAs (110) and GaN (110) surfaces. Our results for the (100) surfaces show that, while the (2 × 1) reconstruction is characterized by dimer vibrations, the (1 × 1) reconstruction presents interesting features which is closely related to the reduced mass of the compound. All the studied cases show the presence of a Rayleigh mode. The calculated properties for the (110) surfaces agree very well with the available experimental data from HEELS and inelastic He-atom scattering as well as with other theoretical calculations.
