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We present the first grid of 3D simulations for the pure-helium atmospheresof DB white dwarfs. The simulations were computed with the CO5BOLDradiation-hydrodynamics code and cover effective temperatures and surfacegravities between 12000 K < Teff < 34000 K and 7.5 < log(g) (cgs units) < 9.0,respectively. In this introductory work, synthetic spectra calculated from the3D simulations are compared to appropriate 1D model spectra under adifferential approach. This results in the derivation of 3D corrections for thespectroscopically derived atmospheric parameters of DB stars with respect tothe 1D ML2/alpha = 1.25 mixing-length parameterisation. No significant Teffcorrections are found for the V777 Her instability strip region, and thereforeno 3D revision is expected for the empirical blue and red edges of the strip.However, large log(g) corrections are found in the range 12000 K < Teff < 23000K for all log(g) values covered by the 3D grid. These corrections indicate that1D model atmospheres overpredict log(g), reminiscent of the results found from3D simulations of pure-hydrogen white dwarfs. The next step will be to compute3D simulations with mixed helium and hydrogen atmospheres to comprehend thefull implications for the stellar parameters of DB and DBA white dwarfs.

Pure-helium 3D model atmospheres of white dwarfs