Internal structure of 4 M_⊙ star with Z=0.014 at the moment of He-shell ignition during TP-AGB stage. Here, r is the radial distance from the core and R is the stellar radius. In the upper panel, the values corresponding to the left vertical axis are represented by solid lines, while the dashed lines correspond to the values on the right vertical axis. The lower panel shows D_mix in these zones. The grey shaded area represents the convective zone. L_mix represents the power required to trigger mixing up to this zone.