We compute |E(x)| using (9) at 162 approximately equispaced points on the surface of each nanoparticle (located at the vertices of an icosphere) and designate the point with the largest |E| as the hotspot. E hot is averaged over incident polarizations E 0 = êx , êy , and êz . For E hot,i , the three independent polarizations are included together in one data set of size 3N .