All-electron versus pseudopotential calculation of optical properties: Thecase of GaAs

Tnt reliability of the widespread practice of calculating the optical prope rties of solids using pseudo wavefunctions instead of the true electron wav efunctions has been tested in the case of bulk GaAs. Pseudopotential calcul ations of the imaginary part of the dielectric function - where the matrix elements of the momentum operator are calculated between pseudo wavefunctio ns - have been compared with all-electron full-potential linear muffin-tin orbital calculations where the true wavefunctions are used. No evidence has been found of differences due to the different sets of wavefunctions emplo yed in the two approaches.