Averaged abundance trends from Fig. 3 (green bullets), compared to the predictions from stellar structure models including atomic diffusion with additional mixing with two different efficiencies, at an age of 13.5 Gyr. Horizontal, dashed lines represent the initial abundances of the models, which have been adjusted so that predictions match the observed abundance level of the coolest stars. The groups of three arrows in each panel indicate the influence on averaged abundances from increasing the effective temperature by 40 K (left), surface gravity by 0.1 dex (middle) and microturbulence by 0.1 km s^-1 (right) – see also Table 5.