Dependence of Z_center on (a) A₂, (b) t_acc, (c) f_overshoot, and (d) planet formation models (corresponding to different values of M₁, M₂, and Z_acc,max; see Table 4). In panel a, the results of models K2 and K2-MZvar are shown, in addition to those of models K2′, K2-MZ1′, and K2-MZ8′, with f_overshoot = 0.01 and t_acc = 10 Myr (see Table 1). In panels b and c, the green and orange curves indicate models K2′ and K2-MZ1′, respectively. The orange dots in panel d are the K2-MZ simulation results. The two horizontal gray dashed lines in all the panels denote the results of the non-accreting models without overshooting for the GS98 (top) and AGSS09 (bottom) compositions. The horizontal green dashed line in panel d denotes the result of model K2′ with A₂ = 0.12, t_acc = 5 Myr, and f_overshoot = 0.01.