Variation of thermohaline diffusion coefficient within the radiative region, at five typical stages along the evolution of a selected star, 0.78 M_⊙. The x-axis is the relative mass in Eq. (4). Models with different thermohaline efficiency parameters, α_th = 50, 100, 150, (referred to as ‘TEP’) are displayed with different line styles, while colours indicate the five stages: at the base of the RGB (BASE), 0.5 dex below the bump’s luminosity (Lb-0.5), at the bump’s luminosity (BUMP), 0.5 dex above the bump (Lb+0.5), 1 dex above the bump (Lb+1), and at the tip of the RGB (TRGB).