  Convective motions in solar-type stellar atmospheres induce Doppler shifts
that affect the strengths and shapes of spectral absorption lines and create
slightly asymmetric line profiles. 1D LTE studies of elemental abundances are
not able to reproduce this phenomenon, which becomes particularly important
when modeling the impact of isotopic fine structure, like the subtle depression
created by the 6Li isotope on the red wing of the Li I resonance doublet line.
The purpose of this work is to provide corrections for the lithium abundance,
A(Li), and the 6Li/7Li ratio that can easily be applied to correct 1D LTE
lithium abundances in G and F dwarf stars of approximately solar mass and
metallicity for 3D and non-LTE (NLTE) effects. The corrections for A(Li) and
6Li/7Li are computed using grids of 3D NLTE and 1D LTE synthetic lithium line
profiles, generated from 3D hydro-dynamical CO5BOLD and 1D hydrostatic model
atmospheres, respectively. The 3D NLTE corrections are then approximated by
analytical expressions as a function of the stellar parameters. These are
applied to adjust the 1D LTE isotopic lithium abundances in two solar-type
stars, HD 207129 and HD 95456. The derived 3D NLTE corrections range between
-0.01 and +0.11 dex for A(Li), and between -4.9 and -0.4% for the 6Li/7Li
ratio, depending on the adopted stellar parameters. In the case of the 6Li/7Li
ratio, our corrections are always negative, showing that 1D LTE analysis can
significantly overestimate (up to 4.9 percentage points) the presence of 6Li in
the atmospheres of solar-like dwarf stars. These results emphasize the
importance of reliable 3D model atmospheres combined with NLTE line formation
for deriving precise isotopic lithium abundances. Although 3D NLTE spectral
synthesis implies an extensive computational effort, the results can be made
accessible with parametric tools like the ones presented in this work.
