Top: size distributions of the dust mixtures from THEMIS (parameters are listed in Table A.1) for CM-grains, i.e. diffuse ISM-like dust (grey line), AMM (blue line), and AMMI (orange line), i.e. grain aggregates typical of starless dense clouds. The black line, the dotted line, and the dash-dotted line correspond to a-C, a-C:H/a-C, and a-Sil/a-C respectively, which are the sub-components of the CM grains. Bottom: associated spectra, computed with DustEM with a radiation field corresponding to a star at 34 600 K with G₀ = 100.