A comparativeab initiostudy of collective dynamics in Al₉₀Si₁₀and Al₉₀Mg₁₀liquid alloys

Dispersion of acoustic and optic collective excitations are comparatively studied in two Al-based liquid metallic alloys, which contain ten atomic percent of Si with four valence electrons or Mg with two ones. Partial density-density and current-current time correlation functions are analyzed by a combination ofab initiomolecular dynamics simulations and theoretical generalized collective modes approach. We obtain and analyze the dispersion of acoustic and optic collective excitations and wave number dependence of the slowest relaxation process as eigenmodes of the generalized Langevin equation in matrix form. These findings allow understanding of different factors responsible for features in collective dynamics of the two liquid metallic alloys.