The optical extinction spectra of the gels also depend on salt concentration (Fig. ), providing complementary information to help understand their structures. At higher [TBAPF 6 ], the extinction broadens and redshifts. We use MPM to test whether coarsening can explain these changes. ITO nanocrystals in this size range are known to have a radially varying free electron concentration, so we model their dielectric function with a Drude-type plasmonic core and a dielectric shell, complexity easily incorporated into MPM. As before, the parameters describing the dielectric function are determined by fitting the LSPR spectrum of a dilute nanocrystal dispersion (Fig. , Tables and). At each of six stages of coarsening from the Brownian dynamics trajectory, we use MPM to compute the polarization-averaged extinction spectrum for the 64000-nanoparticle configuration (Fig. ). The simulations reproduce the asymmetric broadening observed experimentally, while other candidate microstructures like cluster fluids with similar trends in S show the opposite optical broadening trends (Fig. ).