Composition profiles for the inner ejecta of model a2 used in the initial CMFGEN model at 1.1 d (the dashed curve corresponds to ⁵⁶Ni). The outer ejecta has the same composition as the one at 4000 km s⁻¹. The total ejecta mass for model a2 is 14.30 M_⊙. Other models have similar profiles because they all stem from the same progenitor. Differences arise from differences in explosion energy, ⁵⁶Ni yield, and mixing. Hence, other models show composition profiles that are shifted horizontally (i.e., in velocity space) or vertically (i.e., in yield, which is most relevant for ⁵⁶Ni, or for H and He in model a4he; see Sect. 3.2 for discussion).