Simulation of mixed nanocrystal superlattices. N = 11600 spherical nanoparticles of radius a were placed on a two-dimensional hexagonal lattice of area fraction 0.87 on the z = 0 plane inside a triply-periodic box, with a length of 50a in the z-direction normal to the lattice plane. Particles were randomly assigned to one of two %Sn dopant concentrations in proportion to the intended mixing fraction, with simple Drude dielectric functions described in Table . Two MPM simulations were performed for E 0 = E 0 êj (j = x, y). The average dipole for each polarization was then computed p j = i p ij /N = p j e j and averaged over field polarizations p = ( p x + p y )/2. This process was repeated and p averaged over a total of 20 independently prepared lattices. The fraction of incident light transmitted T for the superlattices when placed on a 500 µm thickness silicon substrate is then computed from p through the procedure described in Supporting Information Sec. 4.2 and extinction reported aslog T .