Figure 4

Magnitude of the electric field enhancement factor near the sharp tip of a prolate Ag spheroid with semiaxes a = 10 nm and c = 40 nm. Panels marked “REF” are reference results obtained by differentiating Eq. 3; “CM” and “LEC” indicate the results of DDA-based simulations employing CM and LEC polarizabilities, respectively. The DDA-based simulations use N = 24679 subunits of edge length d = 0.879 nm to model the spheroid; the colored squares in the legend at the bottom of the figure are scaled to have the same edge length