  Recent developments in the three-dimensional (3D) spectral synthesis code
Linfor3D have meant that, for the first time, large spectral wavelength
regions, such as molecular bands, can be synthesised with it in a short amount
of time. A detailed spectral analysis of the synthetic G-band for several dwarf
turn-off-type 3D atmospheres (5850 <= T_eff [K] <= 6550, 4.0 <= log g <= 4.5,
-3.0 <= [Fe/H] <= -1.0) was conducted, under the assumption of local
thermodynamic equilibrium. We also examine carbon and oxygen molecule formation
at various metallicity regimes and discuss the impact it has on the G-band.
Using a qualitative approach, we describe the different behaviours between the
3D atmospheres and the traditional one-dimensional (1D) atmospheres and how the
different physics involved inevitably leads to abundance corrections, which
differ over varying metallicities. Spectra computed in 1D were fit to every 3D
spectrum to determine the 3D abundance correction. Early analysis revealed that
the CH molecules that make up the G-band exhibited an oxygen abundance
dependency; a higher oxygen abundance leads to weaker CH features. Nitrogen
abundances showed zero impact to CH formation. The 3D corrections are also
stronger at lower metallicity. Analysis of the 3D corrections to the G-band
allows us to assign estimations of the 3D abundance correction to most dwarf
stars presented in the literature. The 3D corrections suggest that A(C) in CEMP
stars with high A(C) would remain unchanged, but would decrease in CEMP stars
with lower A(C). It was found that the C/O ratio is an important parameter to
the G-band in 3D. Additional testing confirmed that the C/O ratio is an equally
important parameter for OH transitions under 3D. This presents a clear
interrelation between the carbon and oxygen abundances in 3D atmospheres
through their molecular species, which is not seen in 1D.
