  We construct a 3D radiative-hydrodynamic model atmosphere of parameters Teff
= 4820 K, log g = 4.5, and solar chemical composition. The theoretical line
profiles computed with this model are asymmetric, with their bisectors having a
characteristic C-shape and their core wavelengths shifted with respect to their
laboratory values. The line bisectors span from about 10 to 250 m/s, depending
on line strength, with the stronger features showing larger span. The
corresponding core wavelength shifts range from about -200 m/s for the weak Fe
I lines to almost +100 m/s in the strong Fe I features. Based on observational
results for the Sun, we argue that there should be no core wavelength shift for
Fe I lines of EW > 100 mA. The cores of the strongest lines show contributions
from the uncertain top layers of the model, where non-LTE effects and the
presence of the chromosphere, which are important in real stars, are not
accounted for. The comparison of model predictions to observed Fe I line
bisectors and core wavelength shifts for a reference star, HIP86400, shows
excellent agreement, with the exception of the core wavelength shifts of the
strongest features, for which we suspect inaccurate theoretical values. Since
this limitation does not affect the predicted line equivalent widths
significantly, we consider our 3D model validated for photospheric abundance
work.
