Distribution of micro-turbulence for models with solar abundances for different effective temperatures T_eff and surface gravities log   g (colour-coded). We had to disable the convection for the giants with T_eff ≳ 5500 K and therefore no micro-turbulence was applied to these spectra. In and around this area we observe numerical instabilities causing single models to show differing results. Over-plotted are observational data points taken from Landstreet et al. (2009) (+) and Takeda et al. (2008) (×).