Influence of the number of monomers for a-Sil_Fe,FeS (left panels), a-C (middle panels), and a-C:H (right panels) aggregates made of compact spherical monomers with radius a₀ = 0.1 μm and N = 1, 2, 4, 6, 8, 10, 12, 14, and 16 monomers plotted in blue, pink, green, fuchsia, red, yellow, silver, brown, and orange, respectively. Top bottom panels: Q_abs (N, λ), Q_sca (N, λ), the ratio of the latter to κ(N = 1, λ) for an isolated compact spherical grain with a = a₀.