] provided a better fit. The relative permittivity of the inclusions was set to 12.7, and the method outlined in Sec. S6 was used to calculate polarizabilities. It is important to ascertain how a continuum model for these nanocomposites can capture these effects. The first phenomenon, that the polarizable nanoparticle generates an induced field which increases polarization in the surrounding matrix, is already qualitatively present in any continuum model with a dielectric ellipsoid with permittivity ε ell in a polarized dielectric matrix with permittivity ε mat , when ε ell > ε mat . Nevertheless, there will be a quantitative difference in the screening of this this induced field by the surrounding ions in the atomic model than by a continuum dielectric. In addition, Fig. already shows that the continuum model of a dielectric sphere in matrix cannot reproduce the high polarization exhibited in quantum simulations. We believe this shortcoming is in large part explained by the greater electronic delocalization and coupling of the ionic dynamics of O and Ag at the interface.