Predictions for the variations of atmospheric abundances relative to the initial composition for a 0.77 M_⊙ star with ﹩[ \mathrm{Fe}\,/ \mathrm{H}\,] =-2﹩ that reaches the TOP after 13.5 Gyr. Different symbols/line styles represent different model treating: atomic diffusion including radiative acceleration ﹩g_{\mathrm{rad}\,}﹩ (filled circles); atomic diffusion without radiative acceleration (rhombi); atomic diffusion including radiative acceleration and turbulent mixing T6.0 (triangles and solid line); atomic diffusion without radiative acceleration, but with turbulent mixing T6.0 (triangles and dashed line). For details, see § 4 and Richard et al. (2002).