  The theoretical prediction of micro- and macroturbulence (xi_mic and xi_mac)
as a function of stellar parameters can be useful for spectroscopic work based
on 1D model atmospheres in cases where an empirical determination of xi_mic is
impossible due to a lack of suitable lines and/or macroturbulence and
rotational line broadening are difficult to separate. In an effort to exploit
the CIFIST 3D model atmosphere grid for deriving the theoretical dependence of
xi_mic and xi_mac on effective temperature, gravity, and metallicity, we
discuss different methods to derive xi_mic from the numerical simulations, and
report first results for the Sun and Procyon. In both cases the preliminary
analysis indicates that the microturbulence found in the simulations is
significantly lower than in the real stellar atmospheres.
