Overview of the grid of CO5BOLD 3D model atmospheres adopted for the computation of the fitting functions. The green filled squares mark the models that have been used in this work (five different metallicities, see legend at upper left), the grey squares indicate existing models that are part of the CIFIST grid but have not been considered in the present context. The blue squares highlight the missing models for which abundance corrections were derived by extrapolation (see Sect. 3.2). The solar 3D CO5BOLD model is indicated by the Sun symbol.