Context : 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 .
One-dimensional ( 1D ) local thermodynamic equilibrium ( 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 \mathrm { { } ^ { 6 } Li } isotope on the red wing of the Li i resonance doublet line .

Aims : The purpose of this work is to provide corrections for the lithium abundance , A ( \mathrm { Li } ) , and the \mathrm { { } ^ { 6 } Li / ^ { 7 } Li } 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 three-dimensional ( 3D ) and non-LTE ( NLTE ) effects .

Methods : The corrections for A ( \mathrm { Li } ) and \mathrm { { } ^ { 6 } Li / ^ { 7 } Li } are computed using grids of 3D NLTE and 1D LTE synthetic lithium line profiles , generated from 3D hydro-dynamical CO ^ { 5 } BOLD and 1D hydrostatic model atmospheres , respectively .
For comparative purposes , all calculations are performed for three different line lists representing the Li i \lambda 670.8 nm spectral region .
The 3D NLTE corrections are then approximated by analytical expressions as a function of the stellar parameters ( { T _ { eff } } , \log g , \mathrm { [ Fe / H ] } , v \sin i , A ( \mathrm { Li } ) , \mathrm { { } ^ { 6 } Li / ^ { 7 } Li } ) .
These are applied to adjust the 1D LTE isotopic lithium abundances in two solar-type stars , HD 207129 and HD 95456 , for which high-quality HARPS observations are available .

Results : The derived 3D NLTE corrections range between -0.01 and +0.11 dex for A ( \mathrm { Li } ) , and between -4.9 and -0.4 % for the \mathrm { { } ^ { 6 } Li / ^ { 7 } Li } ratio , depending on the adopted stellar parameters .
We confirm that the inferred \mathrm { { } ^ { 6 } Li } abundance depends critically on the strength of the Si i 670.8025 nm line .
Our findings show a general consistency with recent works on lithium abundance corrections .
After the application of such corrections , we do not find a significant amount of \mathrm { { } ^ { 6 } Li } in any of the two target stars .

Conclusions : In the case of the \mathrm { { } ^ { 6 } Li / ^ { 7 } Li } ratio , our corrections are always negative , showing that 1D LTE analysis can significantly overestimate the presence of \mathrm { { } ^ { 6 } Li } ( up to 4.9 percentage points ) 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 .