Internal distribution of Fe and Ni together with their relation to g_rad(Fe) and g_rad(Ni) in a 0.5    M_⊙ model with Z₀ = 0.001 for four turbulence strengths, each anchored at a fixed ΔM₀ (see Eqs. (1) and (3)), identified in the upper panel. The solutions labeled  −7.5,  −8 and  −9 are after 32 Myr on the HB, while the solution labeled  − 10 is after 7 Myr. The lower panel gives κ_R as a function of log ΔM/M_⊙. A local maximum of g_rad(Fe) and of κ_R occurs for log ΔM/M_⊙ between  − 10 and  − 9 and corresponds to log T ~ 5.5. When the iron abundance becomes rapidly much higher than solar in contradiction with observations of sdB stars. The function 1/μ₀ is shown (solid lines) for each model in the panel above that for κ_R. In the same panel, the function 1/μ_0eff is shown by dotted lines. It is defined in Sect. 5.3.