S5.1 and Ref. for a full description]. Hally et. al found that for the 216-atom Ag 8 nanocomposite under applied electric field, the change in dipole moment relative to zerofield of the inclusion was 1.221 a.u., compared to a total change in the simulation cell dipole moment of 12.688 a.u. (calculated using Eq. 3 and the values reported for ε r , E, and Ω in Ref. . Thus, the ratio of the inclusion dipole moment to the total cell dipole moment, which we call P r,quant , is 0.0926 for the 216-atom Ag 8 nanocomposite. We used this ratio as a point of comparison with the continuum model of the same 216-atom cell.