Effective nuclear parameters in the neutron-star crust, according to different models, as functions of baryon number density n_b in the crust of a neutron star. Top panel: nuclear mass number A (the middle group of curves), the number of protons in a cluster Z (the lower curves), and the effective Wigner-Seitz cell mass number A′ (the upper curves). Bottom panel: rms charge radius of the nucleus. The results are shown for the models BSk19 (dashed lines and filled dots), BSk20 (dot-dashed lines and open circles), BSk21 (solid lines and filled triangles), and, for comparison, the smooth-composition model (the dotted curves). The left vertical dotted line shows the position of the boundary between the inner and outer crust, n_b = n_d (to the left of this line A′ = A). The right vertical dotted lines mark n_cc, the interface between the crust and the core, in the BSk models. Between these boundaries, the curves represent analytical fits, and the symbols show some of the numerical data.