Polarizability as a function of scattering angles for different mixtures of dust. The polarizability is the ratio of the -S12 over S11 elements of the Mueller matrix. In all cases, dust mixtures have power-law size distributions with a_min = 0.03  μm and a slope of − 3.5. Six cases with increasing values of a_max are considered. The red curves show the polarizability for Mathis & Whiffen (1989) grains (a mix of astrosilicates and amorphous carbon and 80% porosity). The dotted green curves are for pure astronomical silicates with 80% porosity (Draine 2003). The blue dashed curves are for compact astronomical silicates without porosity (Draine 2003). The black curve is for a mixture of compact no porosity grains made of 100% amorphous carbon. All models with porosity have a high polarizability near 90 degrees scattering angles. Models with compact particles show lower maximum polarizations.