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The E 1 c reflectivity has been measured up to 10 eV for hexagonal, single-crystal GaN.The band structure and reflectivity have been computed by the empirical pseudopotential method and used to identify the observed spectral peaks.La rBflectivit6 E 1 c d'un monocristal de GaN hexagonal a 6t6 measure6 jusqu'8 10 eV.La structure de bande et la r6flectivitk ont 6t6 calculkes par la mkthode du pseudopotentiel empirique et ont 8th utiliseks pour identifier les cretes du spectre observ6.

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The empirical pseudopotential method is used to compute the band structure, density of states, and reflectivity of hexagonal zinc oxide. The local approximation is assumed, on the basis of recent photoemission experiments which showed that the zinc core 3d band lies deep below the valence band. The calculation succeeds in identifying the reflectivity peaks, but gives stronger amplitudes than are observed, and these identifications are shown to fit well into the systematics of the other three zinc chalcogenides. Reasonable agreement is also obtained with the experimental locations of the maxima in the density of states and with the large value of the valence bandwidth.La methode des pseudopotentiels empiriques a Bt6 utilisee pour calculer la structure des bandes, la densit6 des 6tats et la reflectivit6 de l'oxide de zinc hexagonal. On suppose une approximation locale, car les resultats recents en photo-6mission ont montre que la bande 3d du zinc est beaucoup plus profonde que la bande de valence. Le calcul reussit B identifier la structure de reflectivite, mais donne des amplitudes plus grandes que celles qui sont observbes, e t ces identifications sont en bon accord avec le systeme des autres trois chalcogenides de zinc. Un accord raisonable est aussi obtenu avec la position des maxima de densite d'btats determinee experimentalement e t avec la grosse largeur de la bande de valence.